AlphaFive
Member
HF3
Well said Sir, I agree with you
Well said Sir, I agree with you
NASA Target AKD Si-Tex Lowe HF3 receiver
- Thread starter nanZor
- Start date
- Status
Simple audio improvement mod
Dug into the radio and noticed that there is the typical polarized electrolytic in the audio path to the speaker.
Replaced the polarized 470uF cap right next to the speaker jack on the board with a BIpolar / non-polarized type and audio is improved.
This is a common modification target for many radios. Normally any audio improvement, like a KIWA upgrade consists of more than one part. It's the SUM of the parts, improved electrolytics, other small caps, metallic film resistors in the dc and audio paths etc.
But if you are only going to do one, then that audio output cap is a must.
Did my mod turn it into hi-fi? NO. But I can tell it is working - not by listening to ssb or cw, but immediately noticed that the *background band noise* is much smoother. And I was able to remove the paper-towel filtering!
To be honest about it - I was expecing a diy-placebo effect, but if you've spent a LOT of intense time listening to your radios, one can tell.
In the end, the main improvement is to a reduction in long-term listener fatigue. And of course enhanced intelligibility, but one might not notice that right away.
At least I know it's working, as it is one of the classic audio-improvement mods from the past when one could actually replace discrete components!
Dug into the radio and noticed that there is the typical polarized electrolytic in the audio path to the speaker.
Replaced the polarized 470uF cap right next to the speaker jack on the board with a BIpolar / non-polarized type and audio is improved.
This is a common modification target for many radios. Normally any audio improvement, like a KIWA upgrade consists of more than one part. It's the SUM of the parts, improved electrolytics, other small caps, metallic film resistors in the dc and audio paths etc.
But if you are only going to do one, then that audio output cap is a must.
Did my mod turn it into hi-fi? NO. But I can tell it is working - not by listening to ssb or cw, but immediately noticed that the *background band noise* is much smoother. And I was able to remove the paper-towel filtering!
To be honest about it - I was expecing a diy-placebo effect, but if you've spent a LOT of intense time listening to your radios, one can tell.
In the end, the main improvement is to a reduction in long-term listener fatigue. And of course enhanced intelligibility, but one might not notice that right away.
At least I know it's working, as it is one of the classic audio-improvement mods from the past when one could actually replace discrete components!
Audio mod update
I KNEW I should have kept notes but alas ...
Normally for LSB the best sound was with the BFO / Clarify control at about 3 oclock. USB was normally the opposite end, about 9 oclock.
I don't use the Clarify control as a general-purpose sweep-tune. I set the bfo to the proper "oclock" position depending on the sideband in use, and do minor tweaks. No whipping that clarify control back and forth - slow knob tunes is what takes care of major frequency changes.
But now, with the bipolar cap installed, I noticed that I have much more "fine tune" range with the bfo than before, where audio would just become too nasally and pinched before. And I'm more easily able to copy stations way down in the noise.
This makes me wonder if that oem audio cap was installed backwards, or the cap was wrapped with the improper polarity, or maybe even a board-silkscreen error?
Whatever it was, the swap to a bipolar (aka non-polarized) 470uf audio output cap is highly recommended for those so inclined.
The original was rated at 16v, but my replacement is only 10v. So far so good, especially since I'm not cranking the audio to marine vessel blasting levels all day. I'll let you know if it smokes.
I KNEW I should have kept notes but alas ...
Normally for LSB the best sound was with the BFO / Clarify control at about 3 oclock. USB was normally the opposite end, about 9 oclock.
I don't use the Clarify control as a general-purpose sweep-tune. I set the bfo to the proper "oclock" position depending on the sideband in use, and do minor tweaks. No whipping that clarify control back and forth - slow knob tunes is what takes care of major frequency changes.
But now, with the bipolar cap installed, I noticed that I have much more "fine tune" range with the bfo than before, where audio would just become too nasally and pinched before. And I'm more easily able to copy stations way down in the noise.
This makes me wonder if that oem audio cap was installed backwards, or the cap was wrapped with the improper polarity, or maybe even a board-silkscreen error?
Whatever it was, the swap to a bipolar (aka non-polarized) 470uf audio output cap is highly recommended for those so inclined.
The original was rated at 16v, but my replacement is only 10v. So far so good, especially since I'm not cranking the audio to marine vessel blasting levels all day. I'll let you know if it smokes.
Last edited by a moderator:
A blast to use during contests believe it or not!
It is hard to explain why I am in love with a receiver (that you can still get new) that came designed back from the 90's basically. Especially during a cw contest!
A silky weighted VFO knob you can twist until the next century without worry. Doesn't get much simpler than a notched / castled vfo backside and an led to generate counts. Spin-n-grin is no worry at all about wear and tear. Seems to have outlasted about 5 vfo's from modern rigs that can't keep up with me...
Quality pots, loud audio - not perfect but totally usable and on and on.
Essentially, the simplicity of expression, but decent performance *for what it is* is what makes it a world-beater compared to ANY recent portable.
Sure, I'm workin' it during the cw contest - spin-n-grin, tweaking the bfo, adjusting the MFJ tuner/amp combo for best results - using my ears to compensate for the wide 3.8khz filter. All being run from solar charged AA-sized lifepo4 batteries from the backyard lighting... Oh, and an on-ground loop antenna described elsewhere here.
Ahhhh -- it's a special kind of fun.
It is hard to explain why I am in love with a receiver (that you can still get new) that came designed back from the 90's basically. Especially during a cw contest!
A silky weighted VFO knob you can twist until the next century without worry. Doesn't get much simpler than a notched / castled vfo backside and an led to generate counts. Spin-n-grin is no worry at all about wear and tear. Seems to have outlasted about 5 vfo's from modern rigs that can't keep up with me...
Quality pots, loud audio - not perfect but totally usable and on and on.
Essentially, the simplicity of expression, but decent performance *for what it is* is what makes it a world-beater compared to ANY recent portable.
Sure, I'm workin' it during the cw contest - spin-n-grin, tweaking the bfo, adjusting the MFJ tuner/amp combo for best results - using my ears to compensate for the wide 3.8khz filter. All being run from solar charged AA-sized lifepo4 batteries from the backyard lighting...
Oh, and an on-ground loop antenna described elsewhere here.Ahhhh -- it's a special kind of fun.
Uniden BC20 non-amplified speaker - good fit
Got around to wiring up a Uniden non-amplified BC20 external speaker to the rig and can recommend it. I'm sure others would work just fine, but I had the BC20 on hand.
Note to Uniden - my BC20 is NOT AMPLIFIED. I don't know if it was in the past, but that makes for a lot of confusion about it in the marketplace! I'm sure many who want a passive speaker pass up the BC20 due to wrong info about it.
The receiver has way more than enough audio to drive this comfortably. Situated on top of the receiver, the u-shaped mobile bracket slips down into one of the speaker grill cutouts to provide a somewhat stable loose mount - even when the receiver is tilted back.
The BC20 is large enough to provide just that extra bit of low end response, as compared to some puky little speaker, but certainly not as much low end as the oem speaker. And that's ok for comms use. AM BCB still sounds ok on it. Since there is not much of a surround, and with the highs and lows sloped off a bit, the sound is more focused, yet still high quality fidelity. CW especially has more presence, but it doesn't aggravate. Compared to the oem speaker, you may end up actually turning the gain down, improving the audio s/n ratio.
Uniden's "noise filter" on the speaker is a resistive network, rather than an LC network, and really does slice off just a tad of the high-end . They didn't over-do it, so thumbs up for being actually useful. And, no change in audio volume level was necessary to compensate.
Nothing gets around the fact that on ssb, the 3.8khz filter is almost barn door wide. But when bands are quiet, and you aren't trying to listen to the SSB Sweepstakes contest, you can listen "through" with Unidens noise-filter to avoid a bit of long-term fatigue. Basically it sound similar to when I crank a Kenwood 590's filter up to 4K.
Someday I'll get around to putting in a sharper ssb filter, and a REAL external speaker jack, but for now I'm pleased with the Uniden BC20 and HF3 receiver combo.
Got around to wiring up a Uniden non-amplified BC20 external speaker to the rig and can recommend it. I'm sure others would work just fine, but I had the BC20 on hand.
Note to Uniden - my BC20 is NOT AMPLIFIED. I don't know if it was in the past, but that makes for a lot of confusion about it in the marketplace! I'm sure many who want a passive speaker pass up the BC20 due to wrong info about it.
The receiver has way more than enough audio to drive this comfortably. Situated on top of the receiver, the u-shaped mobile bracket slips down into one of the speaker grill cutouts to provide a somewhat stable loose mount - even when the receiver is tilted back.
The BC20 is large enough to provide just that extra bit of low end response, as compared to some puky little speaker, but certainly not as much low end as the oem speaker. And that's ok for comms use. AM BCB still sounds ok on it. Since there is not much of a surround, and with the highs and lows sloped off a bit, the sound is more focused, yet still high quality fidelity. CW especially has more presence, but it doesn't aggravate. Compared to the oem speaker, you may end up actually turning the gain down, improving the audio s/n ratio.
Uniden's "noise filter" on the speaker is a resistive network, rather than an LC network, and really does slice off just a tad of the high-end . They didn't over-do it, so thumbs up for being actually useful. And, no change in audio volume level was necessary to compensate.
Nothing gets around the fact that on ssb, the 3.8khz filter is almost barn door wide. But when bands are quiet, and you aren't trying to listen to the SSB Sweepstakes contest, you can listen "through" with Unidens noise-filter to avoid a bit of long-term fatigue. Basically it sound similar to when I crank a Kenwood 590's filter up to 4K.
Someday I'll get around to putting in a sharper ssb filter, and a REAL external speaker jack, but for now I'm pleased with the Uniden BC20 and HF3 receiver combo.
Last edited by a moderator:
pjxii
Member
I appreciate the detail you put into your posts, Hertz!
On the subject of filter width, I am kind of the opposite with SSB bandwidth. I actually prefer a wider filter (but then I don't listen to contests). I once had a Sony ICF-6800WA (Orange version) but quickly resold it because of the "better" filters and much prefer my White version with the 9 kHz AM wide and 4 kHz AM Narrow/SSB filters. I guess I've learned to mentally filter out any slop from adjacent signals when listening to ham bands, it really doesn't bother me. Now for longwave NDB hunting, that's a different story, which the '6800 doesn't cover anyway...
No problem - it's a lot of fun, and if it helps out a lurker go beyond the usual thumbs-up or thumbs-down review, so much the better.
I have to keep it in perspective too with the filter. This isn't a contest radio, so I have to resist the temptation to try and turn it into one and fail.
What it is though is the best performing portable-dressed-as-a-desktop type of radio. And the ONLY one in this class that has an AGC to handle both cw and ssb properly. All my later purchases with various dsp based receivers fail badly here. I think back in the day, this handling of AGC properly with this type of simplistic circuitry was a tour-de-force.
I kind of laugh when I see all the "Masterpiece of engineering" sales literature. When looked at with the proper glasses on, it actually is!
It's a portable, which are already prone to overload - so it is purposely not as sensitive as it could be. Check.
Acts like a desktop - since the adaptive-speed VFO is going to get a workout, then it better be reliable. Check.
Two smooth operating pots. Simple lcd power-sipping display. Good audio. SSB filter kinda' wide at 3.8k. Ok, would have preferred 2.4k, but this wasn't marketed for use specifically to amateurs / utility hunters, but normal people that might be a little off frequency, hear the garble, and fine tune.
I think the original engineer had all this in mind from a systems concept, rather than peak one area of performance and have it fail spectacularly.
From a battery-current to price standpoint, still the best performance I've ever gotten from 150ma of current draw.
I have to keep it in perspective too with the filter. This isn't a contest radio, so I have to resist the temptation to try and turn it into one and fail.
What it is though is the best performing portable-dressed-as-a-desktop type of radio. And the ONLY one in this class that has an AGC to handle both cw and ssb properly. All my later purchases with various dsp based receivers fail badly here. I think back in the day, this handling of AGC properly with this type of simplistic circuitry was a tour-de-force.
I kind of laugh when I see all the "Masterpiece of engineering" sales literature. When looked at with the proper glasses on, it actually is!
It's a portable, which are already prone to overload - so it is purposely not as sensitive as it could be. Check.
Acts like a desktop - since the adaptive-speed VFO is going to get a workout, then it better be reliable. Check.
Two smooth operating pots. Simple lcd power-sipping display. Good audio. SSB filter kinda' wide at 3.8k. Ok, would have preferred 2.4k, but this wasn't marketed for use specifically to amateurs / utility hunters, but normal people that might be a little off frequency, hear the garble, and fine tune.
I think the original engineer had all this in mind from a systems concept, rather than peak one area of performance and have it fail spectacularly.
From a battery-current to price standpoint, still the best performance I've ever gotten from 150ma of current draw.
pjxii
Member
It looks like the next version of this receiver had a narrower SSB filter and also good performance. Here's a translated review from shortwaveradio.ch
https://translate.googleusercontent...700201&usg=ALkJrhiuPaVGt4l61iqRa1RGLEX8yrn_JA
https://translate.googleusercontent...700201&usg=ALkJrhiuPaVGt4l61iqRa1RGLEX8yrn_JA
Thanks for that link to the newer receivers!
Yeah, I'd like a 2.6k ssb filter, and perhaps a quieter mixer.
The HF3/W I have is actually newer than those, circa 2015 or so. 10 channel memories, but I mostly use that for jumping broadly from band to band. Mostly surface mount replacements of resistors and caps, but there are a few discrete things like coils, less of a rats nest of wiring, and very good soldering of rohs compliant components. 3.8K filter, but wonder if the newer units incoporate the better mixer?
I dug around and saw that there was also a 4E-S model. 20 memories.
It is a really unique thing that these are still being produced basically new 23 years after introduction with several "Mark xx" nomenclatures inside.
Yeah, I'd like a 2.6k ssb filter, and perhaps a quieter mixer.
The HF3/W I have is actually newer than those, circa 2015 or so. 10 channel memories, but I mostly use that for jumping broadly from band to band. Mostly surface mount replacements of resistors and caps, but there are a few discrete things like coils, less of a rats nest of wiring, and very good soldering of rohs compliant components. 3.8K filter, but wonder if the newer units incoporate the better mixer?
I dug around and saw that there was also a 4E-S model. 20 memories.
It is a really unique thing that these are still being produced basically new 23 years after introduction with several "Mark xx" nomenclatures inside.
Lithium powerbank test
Since the HF3 only pulls about 150ma in normal operation, thought I'd try my luck mating it up with an Anker cellphone powerbank, and a little Drok 5 to 9/12v upconverter.
(NOTE: *verified* that the voltage polarity wasn't wired backwards by accident at the Drok factory before I let it touch the HF3)
Works fine. Not much noise except for perhaps a teeny spot here and there across the spectrum. I expected far worse, so this is totally usable. The Drok converter came with the proper sized dc plug for a direct fit, although I'll be doing it right using a fused cable.
Had to manually tap-start the powerbank, and then turn on the receiver. Normal for a smart powerbank when it senses no current draw to have to manually start it. And when I power off the receiver, the Drok converter switches off too, and sensing no current, the Anker battery goes back to sleep.
The Drok 5 to 9 or 12v converter (1a max) uses about 100ma of current on it's own, so the total is really about 250ma - actually 275ma once I power up the MFJ tuner / preamp too. (that current is measured at the 5v output prior to the converter)
Kind of a neat solar solution too - I use a 28 watt folding solar panel to charge the Anker, and in turn use that later to operate the gear.
Since the HF3 only pulls about 150ma in normal operation, thought I'd try my luck mating it up with an Anker cellphone powerbank, and a little Drok 5 to 9/12v upconverter.
(NOTE: *verified* that the voltage polarity wasn't wired backwards by accident at the Drok factory before I let it touch the HF3)
Works fine. Not much noise except for perhaps a teeny spot here and there across the spectrum. I expected far worse, so this is totally usable. The Drok converter came with the proper sized dc plug for a direct fit, although I'll be doing it right using a fused cable.
Had to manually tap-start the powerbank, and then turn on the receiver. Normal for a smart powerbank when it senses no current draw to have to manually start it. And when I power off the receiver, the Drok converter switches off too, and sensing no current, the Anker battery goes back to sleep.
The Drok 5 to 9 or 12v converter (1a max) uses about 100ma of current on it's own, so the total is really about 250ma - actually 275ma once I power up the MFJ tuner / preamp too. (that current is measured at the 5v output prior to the converter)
Kind of a neat solar solution too - I use a 28 watt folding solar panel to charge the Anker, and in turn use that later to operate the gear.
DRAT - When the 40m band went long and quiet, I *can* hear the little buck-boost regulator. Barely, but now that I know it's there, I can't take a step backwards.
Thinking it might be a bit of ripple making it past the dc input filter cap, rather than anything reaching my loop on the ground. We'll work on it, but for now, back to a 2-step process of charging the Anker via solar, and then using that to charge smaller li-ion batts for direct-dc powering. Oh well..
Thinking it might be a bit of ripple making it past the dc input filter cap, rather than anything reaching my loop on the ground. We'll work on it, but for now, back to a 2-step process of charging the Anker via solar, and then using that to charge smaller li-ion batts for direct-dc powering. Oh well..
Gentle reminder for amateurs
Gosh, I still see these things tuned up wrong so just a reminder to avoid out of box disappointment:
The HF3 IF passband out of the box is tuned primarily for USB, with LSB being a "novelty" to boaters who might want to "listen in" on amateurs on the low bands. We can fix that.
Yet I still see them being tuned wrong, just crashing into the bands, and wildly swinging the clarifier knob. This rig does not have any automatic offsets, and leaving the clarifier in the middle and slowly tuning is not the greatest either.
So for USB use:
* Turn the clarifier to about 9 to 10 oclock. Slowly tune the VFO knob to get close to good sound. Now slightly adjust the clarifier.
Don't be freaked out if you are "not on freq" as per the display. You may be 1 khz off in the display - but that is due to the manual offset needed for best tuning. This is not a "big rig".
LSB use:
Turn the clarifier to about 2 to 3 oclock. Turn VFO dial slowly for best sound. Again, your dial may be 2 khz off freq. Slightly adjust the clarifier.
The major emphasis here is to tune for best sound, and not go bananas about being *exactly* on freq in the display.
AMATEURS:
Out of the box, the emphasis on USB usage means that if you tune to some background noise, and switch between usb and lsb, and rotate the clarifier, you may notice a pretty big difference in overall background noise pitch between usb and lsb as you move the clarifier around.
Since I listen to both usb and lsb, I'd rather have a similar sound to the clarifier swings, rather than be close to an exact frequency in the display. See the golden-screwdriver notes below.
CW Ops:
This isn't a contest rig, and that wide 3.8k filter means you hear a lot of stations. One tip is to use tuning along with the clarifier to put an offending station out of the passband. Example:
If you have trouble with a neighboring cw signal, move the vfo up or down 1 khz, and retune the clarifier, not so much to make your desired signal sound great, but to knock the offender out of the passband. Sure you may end up copying your desired station with a much higher or lower pitch than desired, but at least the qrm is under control. Move it another 1K up or down and try again. When it works, it's a lot of fun.
** The GOLDEN SCREWDRIVER WARNING: **
By putting the clarifier in the center position, and *every so slightly* adjusting TC2 trimmer cap (usually with a red friction surround), you can get usb and lsb clarifier swing pitch to sound similar. Check the overall swing of the clarifier sound after adjustment between usb and lsb to make sure you haven't gone too far.
Needless to say, you'll want to mark the oem setting with a fine felt marker before you do this.
I kind of don't like putting this golden-screwdriver info out there, but do it to make it more enjoyable for amateurs to use, and secondly, to possibly recover from a used model that someone has gotten their grubby screwdriver into, so that you may return it to a somewhat normal state.
If they have also tweaked the IF transformers, you could end up with some real junk that needs more professional retuning unless you absolutely know what you are doing. Obsessing about being exactly on frequency in the display can make some want to do this and really tweak it badly.
Gosh, I still see these things tuned up wrong so just a reminder to avoid out of box disappointment:
The HF3 IF passband out of the box is tuned primarily for USB, with LSB being a "novelty" to boaters who might want to "listen in" on amateurs on the low bands. We can fix that.
Yet I still see them being tuned wrong, just crashing into the bands, and wildly swinging the clarifier knob. This rig does not have any automatic offsets, and leaving the clarifier in the middle and slowly tuning is not the greatest either.
So for USB use:
* Turn the clarifier to about 9 to 10 oclock. Slowly tune the VFO knob to get close to good sound. Now slightly adjust the clarifier.
Don't be freaked out if you are "not on freq" as per the display. You may be 1 khz off in the display - but that is due to the manual offset needed for best tuning. This is not a "big rig".
LSB use:
Turn the clarifier to about 2 to 3 oclock. Turn VFO dial slowly for best sound. Again, your dial may be 2 khz off freq. Slightly adjust the clarifier.
The major emphasis here is to tune for best sound, and not go bananas about being *exactly* on freq in the display.
AMATEURS:
Out of the box, the emphasis on USB usage means that if you tune to some background noise, and switch between usb and lsb, and rotate the clarifier, you may notice a pretty big difference in overall background noise pitch between usb and lsb as you move the clarifier around.
Since I listen to both usb and lsb, I'd rather have a similar sound to the clarifier swings, rather than be close to an exact frequency in the display. See the golden-screwdriver notes below.
CW Ops:
This isn't a contest rig, and that wide 3.8k filter means you hear a lot of stations. One tip is to use tuning along with the clarifier to put an offending station out of the passband. Example:
If you have trouble with a neighboring cw signal, move the vfo up or down 1 khz, and retune the clarifier, not so much to make your desired signal sound great, but to knock the offender out of the passband. Sure you may end up copying your desired station with a much higher or lower pitch than desired, but at least the qrm is under control. Move it another 1K up or down and try again. When it works, it's a lot of fun.
** The GOLDEN SCREWDRIVER WARNING: **
By putting the clarifier in the center position, and *every so slightly* adjusting TC2 trimmer cap (usually with a red friction surround), you can get usb and lsb clarifier swing pitch to sound similar. Check the overall swing of the clarifier sound after adjustment between usb and lsb to make sure you haven't gone too far.
Needless to say, you'll want to mark the oem setting with a fine felt marker before you do this.
I kind of don't like putting this golden-screwdriver info out there, but do it to make it more enjoyable for amateurs to use, and secondly, to possibly recover from a used model that someone has gotten their grubby screwdriver into, so that you may return it to a somewhat normal state.
If they have also tweaked the IF transformers, you could end up with some real junk that needs more professional retuning unless you absolutely know what you are doing. Obsessing about being exactly on frequency in the display can make some want to do this and really tweak it badly.
Last edited by a moderator:
Related note:
Even modern-day equipment can sometimes not be offset properly out of the box.
Consider the popular Yaesu FT-857 / 897 line of transceivers. Out of the box, some have been disappointed with the default "thin" sound of either usb or lsb.
From the factory, the usb and lsb RX offsets are at ZERO. Most users are advised to go into the menus, and dial in a + / - offset of at least 1K to make it sound like it should. Not to mention the fact that the ssb filter was default to wide. Heh, kind of sounded like my HF3 when the clarifier was in the total wrong side of the pot!
Of course the dial offsets were spot on, but unless you went into the menu and slid it a little, you had some pretty nasal response. The dial was always accurate, but now your ears are calibrated to the receiver section when you make a small adjustment in the menu.
Even modern-day equipment can sometimes not be offset properly out of the box.
Consider the popular Yaesu FT-857 / 897 line of transceivers. Out of the box, some have been disappointed with the default "thin" sound of either usb or lsb.
From the factory, the usb and lsb RX offsets are at ZERO. Most users are advised to go into the menus, and dial in a + / - offset of at least 1K to make it sound like it should. Not to mention the fact that the ssb filter was default to wide. Heh, kind of sounded like my HF3 when the clarifier was in the total wrong side of the pot!
Of course the dial offsets were spot on, but unless you went into the menu and slid it a little, you had some pretty nasal response. The dial was always accurate, but now your ears are calibrated to the receiver section when you make a small adjustment in the menu.
Last edited by a moderator:
Hi-Pass and Low-Pass filters?
The HF3, like it's more expensive cousin, the Lowe HF-150, has a somewhat open front-end, and can in many circumstances benefit from preselectors, or simple AM bcb notch filters.
In fact, the Lowe offerred a real trick preselector accessory.
I really didn't think I had any problems with AM overload, as I wasn't hearing any bleed-through, or obvious signs of desensitization. Not to mention I'm using a specialized lossy on-ground loop antenna.
So I tried a small Nooelec AM bandstop filter (The "flamingo" enclosed model), usually targeted at the sdr radio market - and guess what? No the heavens didn't suddenly open up, but what DID happen is that my noise floor cleaned up just a little bit. Hey, every bit counts.
I hear the cleaner noise floor whether I place the filter just before the receiver, or even at the input to my MFJ preamp. I'm leaving it in front of the preamp for best effect.
IIRC, very early versions of the HF3 manual made mention that Hi and Low pass filters for the HF bands may be beneficial. Sure enough, for me it was. Of course this means no AM bcb dx'ing, but that's not my main purpose for this rig.
The HF3, like it's more expensive cousin, the Lowe HF-150, has a somewhat open front-end, and can in many circumstances benefit from preselectors, or simple AM bcb notch filters.
In fact, the Lowe offerred a real trick preselector accessory.
I really didn't think I had any problems with AM overload, as I wasn't hearing any bleed-through, or obvious signs of desensitization. Not to mention I'm using a specialized lossy on-ground loop antenna.
So I tried a small Nooelec AM bandstop filter (The "flamingo" enclosed model), usually targeted at the sdr radio market - and guess what? No the heavens didn't suddenly open up, but what DID happen is that my noise floor cleaned up just a little bit. Hey, every bit counts.
I hear the cleaner noise floor whether I place the filter just before the receiver, or even at the input to my MFJ preamp. I'm leaving it in front of the preamp for best effect.
IIRC, very early versions of the HF3 manual made mention that Hi and Low pass filters for the HF bands may be beneficial. Sure enough, for me it was. Of course this means no AM bcb dx'ing, but that's not my main purpose for this rig.
Improved the audio again
Without any real schematic or service manual, I did the unthinkable:
Shot-gunned the rest of the electrolytic caps near the audio amp with non-polarized types. So basically I replaced the 470uf, the 220uf, and the 33uf cap with bipolars. Measured each before install.
No smoke. Sounds good, but not any sort of stereo-showroom improvement. I'm thinking long-term listening pleasure.
The only real immediate indication of the change is that I drop the volume pot below where I usually run it for the same overall output. Perhaps because of a slightly cleaner output. The gap between how my TS590 sounds in 4K bandwidth, and the HF3 is getting closer together.
Without any real schematic or service manual, I did the unthinkable:
Shot-gunned the rest of the electrolytic caps near the audio amp with non-polarized types. So basically I replaced the 470uf, the 220uf, and the 33uf cap with bipolars. Measured each before install.
No smoke. Sounds good, but not any sort of stereo-showroom improvement. I'm thinking long-term listening pleasure.
The only real immediate indication of the change is that I drop the volume pot below where I usually run it for the same overall output. Perhaps because of a slightly cleaner output. The gap between how my TS590 sounds in 4K bandwidth, and the HF3 is getting closer together.
I'm done with audio!
No real surprise, but today ran a small coaxial audio cable with an rca connector to one of those vastly overpriced desktop speakers. The HF3 had no problem driving a Yaesu SP-2000 speaker, and the 3K audio rolloff did the trick.
Despite the wide 3.8k if filter bandwidth, for ssb it really needed a 2.4k audio rolloff. Now it sounds like a real ssb receiver. The HF3 does go down to 100hz, so at times a high pass of 300hz takes the grunge off the low end at times. And of course cranking these filters down all the way makes CW listening even more fun. The headphone jack on the Yaesu SP2K is post-filtration, so that's pretty handy too.
Other passive $speakers like the Yaesu SP-8, the Icom SP-34, SP-41, Kenwood SP-890 should be similar, but at these prices, I like the ones that have the most filter positions available. Crumple a small beach towel and toss it inside the metal cases, and hey - these sound pretty nice.
Not as good as a totally dedicated tunable filter, but these do the job with minimal effort.
No real surprise, but today ran a small coaxial audio cable with an rca connector to one of those vastly overpriced desktop speakers. The HF3 had no problem driving a Yaesu SP-2000 speaker, and the 3K audio rolloff did the trick.
Despite the wide 3.8k if filter bandwidth, for ssb it really needed a 2.4k audio rolloff. Now it sounds like a real ssb receiver. The HF3 does go down to 100hz, so at times a high pass of 300hz takes the grunge off the low end at times. And of course cranking these filters down all the way makes CW listening even more fun. The headphone jack on the Yaesu SP2K is post-filtration, so that's pretty handy too.
Other passive $speakers like the Yaesu SP-8, the Icom SP-34, SP-41, Kenwood SP-890 should be similar, but at these prices, I like the ones that have the most filter positions available. Crumple a small beach towel and toss it inside the metal cases, and hey - these sound pretty nice.
Not as good as a totally dedicated tunable filter, but these do the job with minimal effort.
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