NASA Target AKD Si-Tex Lowe HF3 receiver

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nanZor

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I picked up an unmolested NASA Target HF3 receiver and am pretty pleased with it.

No, it will not be at the top of the Sherwood testing list.

There are a lot of versions of these things out there, basically all the same since about 1998 or so. Nasa Marine, Si-Tex, Target, AKD, even Lowe SRX100. Plenty of reviews out there so I won't just rehash them here.

Mine is a later version that has mostly surface-mount components, aside from the usual filters, transformers, and a small handful of electrolytic caps.

I got it mainly for casual ssb/cw monitoring, and it does quite well even with the wide filter. The ssb filter is an inexpensive 6-pole LT455IT, about 4khz wide. Usable, but in ssb I needed a high frequency audio rolloff, so I just did a simple RC lowpass across the speaker. Without this mod, the high-frequency audio was causing listener fatigue.

This consisted of lifting the positive lead of the speaker wire, and inserting a 10 ohm, 2 watt resistor from the junk-box in series. Directly across the speaker I placed about 15uf of non-polarized caps. Anything from about 4.7 to 20uF should do according to how much you want to rolloff. I actually used what I had on hand - two 22uf polarized electrolytics back to back (negative to negative) giving me 11uf total, and then a 4.7uf bipolar that I had on hand in parallel to that. Not critical, but DO use non-or-bipolar caps for this.

That's more like it. Next to my Kenwood 590s, it is roughly similar to turning off the preamps, and cranking the filters open to about 3 to 3.4k. Without the audio rc rolloff mod, it was just too harsh.

I wanted a bit of lower end boost, so I paralleled a 470uf polarized electrolytic with the last audio output cap on the bottom of the board - although the low end is restricted to the speaker bandwidth itself. But I felt it got me a little bit better midrange response. Probably not necessary for most people.

I'm running a variety of outdoor antennas, like my 33-foot vertical, and in my location, have no major problems. However I have on hand a PAR BCB filter, and an MFJ 1046 passive preselector. So far, I haven't had to use them.

In the end, I have been dissatisfied with most of the low-end radios, like the Grundig 750, Tecsuns and the like, since for *ME*, they overload on even modestly strong signals, or have very poor IF or AF AGC and cover this up with heavy-handed rf attenuation. So far, the Target HF3 is at least trying to act like a bigger radio.

The agc is what I'd call medium. Much like an R75, or Icom 718. I can copy ssb and cw just fine, although of course I'm doing so with a wide filter, so the brain filter will have to be used. Forget contesting - this is a casual rig.

This audio mod is about as far as I'm going to take it. There certainly is the capability for additional mods, like better filters, connectors, backlights and so forth that can be done. In fact, an upgraded "HF4" version is out there that uses a nicer 2.6k ssb filter, so-239 jack, backlighting etc, but may not be as easy to find as an HF3.

It's rated for 300ma, but under my normal listening conditions, I'm drawing no more than about 150-200ma at most.

I had given up on my search for a casual ssb / hf monitoring rx, having been dissatisfied with the Grundig 750, Tecsun's, and others - see my reviews here for why - and feel that the Target HF3 just might be a keeper - with audio mod! I've got to keep it all in perspective at this price / performance level. I have a CommRadio CR1 as well that is getting jealous of this newcomer to my shack, so no hard feelings anybody! :)
 
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nanZor

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Tuning and golden-screwdriver warning!

Resist the temptation to "golden screwdriver" the HF3.

When tuning, the closest you will get to being on frequency is about 1 khz off on the display.

That is, for USB, tune 1 khz higher than normal, and put the clarifier in the 9 o'clock position.

For LSB, tune 1 khz low, and put the clarifier in the 3 o'clock position.

Of course you can just leave it in the center if you like, but you'll now be off by about 2 khz.

There are some guys who try to tweak the display on frequency, and you'll just golden-screwdriver yourself.

Speaking of which, I will admit to a TINY amount of this. After shipping, I noticed a big discrepency between switching between USB and LSB. LSB was very high-pitched no matter where the clarifier was. Maybe it got moved during shipping.

There is no service manual for this radio, although schematics can be found online. I *slightly* tweaked the last IF transformer around the LT455IT filter (closest to the back of the radio) to bring the filter inline for LSB. Note how I said "slightly". Don't go nuts guys. :)
 

ratboy

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I had one of those, the AKD one, about 8 years ago. It was ok, but I didn't like the audio much and sold it. I had/have a bunch of receivers that worked much better and cost about the same. A friend bought it and put it on his boat as a "next to the bed" radio. It died a few years ago. I think he's got a R71a on it now.
 

nanZor

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I can relate to that - initially. Everybody's taste is different.

I'm used to narrow Collins or even higher end Murata filters in my amateur gear. Most of my hobby life with ssb has been with narrow filtering. So initially, the HF3 was kind of in my face with the wide 4khz ssb filter. For AM, it uses a 6khz filter, and as they mention in the manual, that can be kind of muddy for those looking for higher AM fidelity, which requires a wider filter. Aka "Kiwa" filters and such. Or tune maybe 1k off.

I did feel it lacked the proper rolloff in ssb, so I applied a simple RC filter network across the speaker itself. Ah, much better. Still a 4k filter though.

Interestingly enough, I am now using a wider setting with my other HF radios when conditions aren't crowded. I crank my filters up to 3K even! With a bit of training from the RC circuit modified HF3, it doesn't sound so jarring or unnatural anymore!

One thing I disagree with about the manual is "centering" the clarifier. I think many use the clarifier as a wider fine-tune, rather than for *tiny* touch ups. If you go too far in one direction, you get to a weird side of the filter slope which goes tinny - kind of like turning an IF shift control to an extreme in other rigs.

Thus, in USB, use the 7am to 12 O'clock position of the clarifier. For LSB, use the 12 to 5pm o'clock side. This keeps it in the proper side of the filter slope - or so it sounds.

Hopefully your's wasn't "golden screwdriver'd" either. Some guys try to put the display right on frequency by tweaking the oscillator, which is the wrong thing to do since like other radios of the day, it WILL be off by 1-2 khz by design.

I'm getting used to the "box acoustics" of it, and when either my 470 or 1000uF bi-polar caps come in, I'll be replacing the last output speaker coupling capacitor with it. "C64" I believe - I can't remember.

Anyway, for the initial $250 or so radio that it was (now a little more), I'm really drawn to it. It draws only 150 milliamps and is still LOUD. That's about 10 times less than my Kenwood 590. :) And the tuning knob is superb - smooth, fast and self-adjusting for a spin-n-grinner like me. Interestingly enough, the vfo encoder is old old school and may just last a long time, since it uses slots in the knob itself and IR led's I believe to do the chopping. No funky "modern" encoders here. :) Signal level handling and AGC are in a whole different league than the Grundig / Tecsuns (analog OR digital). A "real" radio to me, although one can always push the rig over the edge if they want to.

The weird thing is that initially I was thinking of putting a 2.4 - 2.7khz filter in it for ssb - not any more. My ears have gotten used to the wide bandwidth (no contests obviously), and maybe I'll only take it down to a nicer 3khz ssb filter max. We'll see.

Anyway, I can understand your dislike. I can't STAND my Yaesu 817 qrp rig - the hissy audio drives me up the wall, despite collins filters - something in the audio amp I suppose I'll have to dig into one day. I get mad just looking at it ...
 
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nanZor

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PERFECT SSB audio now:

Took a chance on even more capacitance. 25uF bi-polar across speaker terminals is my sweet spot. (Two 47uf polarized back to back negative-negative, measuring 27uf on Fluke). Convenient. Still using 10 ohm resistor in series with positive red speaker lead.

Didn't muddy up ssb comms. Of course AM which started out a bit muddy, got even worse. I didn't buy this thing for AM however.

Now really close to Kenwood 3K filter response overall in audio response. Not that it fools me, but close enough for comfort.

TIP - got sloppy with soldering and a blob fell into the speaker cone. Fortunately, solder isn't magnetic, so shook that out BEFORE putting cabinet back together so it didn't short anything out.
 

nanZor

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Sensitivity

The HF3 is not particularly sensitive compared to modern rigs. Reviews elsewhere indicate that this might be due to trying to keep things under control with a wide front end in Europe.

I don't know about that, but it does lose sensitivity particularly above 14mhz pretty fast.

I know it isn't a fair comparison, but compared to my Kenwood 590s with all the preamps turned off, there are still plenty of strong signals on the higher bands that are simply just under the noise floor of the HF3. One might think the band is dead, but it is not - assuming there is activity in the first place.

Here, a simple MFJ 1020C tuned preamp with variable +/-10db rf gain really helps. Drug that out of the closet, and presto - the HF3 is much happier. (You might see this as an active antenna, but in my case I unscrewed the little whip, and use it with my own 30 foot vertical.)

Running from a 9V battery right now, it meets my criteria for low-power operation.

Heh, I wouldn't base a new station around this setup, since at some point you'll be pulling so much power with a desk full of boxes, that you might as well be using a more expensive receiver in the first place. :)

Glad I didn't toss the MFJ 1020C, as it is basically unnecessary with my other rigs - but it really did bring the HF3 alive.

On the higher bands, the gain is cranked to max, and that works fine. Lower bands of course don't need a lot of gain. Even though I don't need the preselector tuning in my environment, it surely helps bring a nicer front end to the HF3.
 

nanZor

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Bipolar audio output capacitor

Replaced the existing 470uf polarized 16v cap (right next to the two-pin speaker connector) with a NON-POLARIZED (aka bipolar) 470uf 16v cap. 470uf is enough.

Definitely worth it. The NP cap is bigger than a polarized, so it was mounted flat on the underside of the board where there is plenty of room. Up top, it got too crowded with the speaker basket hitting the new cap.

Tip: If you plan to do both the RC speaker audio rolloff mod and the bipolar cap mod, do the cap mod first. That alone increases fidelity and takes the edge off the wide filter high end in the first place, so you might not need as much capacitance for the RC speaker rolloff mod.

Speaker grill: The speaker grill has openings facing both forwards and backwards. If you have the rig sitting alone on a desk with no surrounding cabinetry, you may want to put a flat or angled reflecting surface off the back of the receiver to reflect the backwards facing slots towards the front. Plenty of audio either way, but a directed sound may be more desirable than an upward facing omni.
 
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nanZor

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Frequency stability mod

In SSB, if your HF3 seems to be jumping around a bit, especially when you turn up the volume or tap on the case, you may have a loose clarifier push-in header, which is practically directly under the speaker.

When fully seated, the 3-wire clarifier terminal connector may not be making the best contact with the pins and can move around a bit. Cleaning with De-Oxit or the like might help, but if there is physical movement, no magic spray will fix that. :)

The easiest mod here is to merely pull back the connector to about half-way inserted, where more pressure is applied to the pins.

If you are running this thing at boom-box levels, then you'll want to rewire the leads from the clarifier pot to the board directly without a connector, and possibly use some hot-glue to keep them absolutely stable.
 
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WA8ZTZ

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Looks like no phones jack is provided. Is there enough real estate on the rear panel to add a phones jack?
 

nanZor

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There is plenty of real-estate for a phone jack. For a hack-job, the case is semi-soft plastic, so you could put one up top pretty easily.

The various versions might have one already - like the HF4, or the Lowe SRX-100. Sci-Tex, Nav-Fax, Garex, AKD, Target and the list seems to go on. Same rig, different owners over the years.

Since about 1997, these things change names a little bit depending on who owns it currently, and small differing editions can be found.

For example, my unit is an HF3/W, which has no speaker jack, but does have a very low level line output to drive some WeFax software, which I'm not using. In addition, the rear-panel attenuator switch is missing. In it's place is a switch to provide power out the antenna jack (normal / active) for active antennas. You might want to be SURE you don't have that activated for normal antenna use if you have this version.
 

nanZor

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I think I'm done for now, unless I want to custom wire a better Murata CFJ series narrowband filter.

Finally ended up with a 1000uF bipolar cap again for the last speaker coupling cap, and swapped in a 10 ohm, 2-watt metal-film resistor instead of the junkbox carbon for the on-speaker rc filter rolloff.

The rig definitely needs to have some preamplification to bring both the signal and noise above the receiver noise-floor, so the MFJ 1020C preamp is here to stay for 14+ mhz reception. The antenna is perfectly tuned with a T-match matchbox, and even with just that, the HF3 still needs a little help on the higher freqs - at least just to light the "1" indicator on the s-meter. That's all I need and it makes a world of difference. Still, the Kenwood has nothing to fear. :)
 

nanZor

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Poor man's Lowe HF-150

After playing with it for a few days, it is really apparent that this is a poor man's Lowe HF-150 stripped of anything costly to produce. No am-sync, rca jacks instead of so-239's, plastic box, inexpensive ceramic wide filter for ssb (4k) and so forth.

Still, it is far more pleasing to me than any portable I have ever used, and although sensitivity and selectivity are not it's strong points, the agc is! It does what it does very well, at only 150ma, and if one wants to take it to the next level, a preselector/tuner/preamp is in order. Just like the HF-150.

Last mods for now ...

Dampened the response of the plastic casing with a thin dense foam covering the bottom of the case. Used a leftover foam pad from a Shorai LFP motorcycle battery spacer, cut to allow room for the cap mods, and the weighted flywheel.

Perfect! The acoustics of the box are highly damped so all I'm hearing now is the speaker for the most part.

Replaced two other electrolytic caps associated with the audio (220uf and 33uf near the original 470uf) with bipolar types. Had to go underneath so as not to hit the speaker basket.

All in all, a very fun, yet capable rig for old-school radio fun with preselectors and whatnot.

It's too bad nothing like this could be profitably produced today, although I throw the gauntlet down at Elecraft to build a rockin BASIC rx with great specs, paying attention to audio (like bipolar caps, metal film resistors, polystrene caps etc etc) without KX3 pricing! :)
 
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nanZor

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Got another one - with easy speaker cabinet!

After an unfortunate need to sell off most of my gear recently, I'm slowly bringing some of it back.

I have an irrational love for the Target HF/3 receiver. Even though for $100 more you can get ten times the receiver with an Alinco R8T.

Right off the bat, I forgot how bad the lack of any real speaker enclosure, and the awful upwards omni-facing speaker sounds. Frequency response is full, but is undirected, leading to harsh reflections from shack walls. Don't kid yourself - this is not a high-end stereo omni. :)

*** Cardboard Speaker Cabinet Mod! ***

Took a 4-inch by 6-inch wide cardboard box, and cut off the top flaps, and one of the 6 inch sides. Placed it over the speaker, and the improvement is great. Looks like a cardboard hot-rod hood-scoop!

Not only is the sound directed forward, but also blocks the high-frequency stuff that would reflect back off the walls and just generally make the radio sound like crap in a room. Win-Win. A BIG improvement with just a few cuts of cardboard.
 

nanZor

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Low Pass / hiss audio filter replacement

MacGyver solution found! You just KNOW you want to play with this receiver....

Who needs r/l/c component filtering? To take the edge off the high freqs while listening to ssb/cw from the wide 4k filter, try folding a paper towel into quarters for a 4-layer filter to go on top of the speaker grill. CW only? Make that about 8 layers.

Takes the edge off without muddying the midrange. Combined with my patented cardboard-box surround, it actually works nicely. Seriously.

And no soldering! :)

From the marketing department:

"Our exclusive multi-layer paper-towl filtering technology, along with the computer-generated carboard box acoustics shaper, reduces long term listener fatigue and enhances legibility. The micro-fibers in the paper towl serve not only to reduce pesky high-frequency response emanating from the speaker, but also reduce and dampen any residual high frequencies that do make it into the acoustic box shaper, further increasing your listening pleasure. All this for $100.00"

Man, what a bargain!

Quite frankly, this is a pretty satisfying solution since the HF-3's don't come with any speaker audio output jacks. I was going add one, or hack up the wefax audio jack, but quite frankly, this towel-n-box combo sounds very similar to my beloved Uniden BC20 comm speaker. I think I'm done!
 
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nanZor

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Mods - I can't help myself ... :)

More words from marketing:

"Our insistance on using paper products ensures the most natural human tones, unsurpassed by metallic, plastic, or mylar surfaces. Our in-house engineers refer to this speaker-to-ear path as being the best going from "cone to cone", which competing products do not truly consider. Get yours today!"

Sorry, but helpful I guess....
 

nanZor

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Final cardboard box speaker mod and tips for similar usage on other rigs with top facing speakers...

Tested various ways to dampen the box further, including putting 4 layers of paper-towl on ALL of the sides eventually and backed off. Here's how it went.

1). Facing into the box, I dampened the rear wall. Good improvement for being directly in front of rig without muddying the midrange.

2) Dampened the top of the box, the side directly opposite the 4 layers of towel over the speaker itself. Very noticeable. As it should, since it is dampening the high freqs making it past the speaker filtering shooting straight up.

3) Went too far by dampening the left and right sides. Things are getting just a tad too "soft".

4) Final configuration is to have the top and rear wall of the box dampened. With the left and right sides left alone, off-axis response is still there when I move down to the other ends of the bench.

Blue painter's tape makes this easy to experiment with.

The funny thing is to be looking into an empty box, and having super nice audio coming out of nowhere, with some *depth* to it !!

I make fun of this project, but only write it up because it is really so pleasant to my ears.

For other radios, the big tip here is that don't just cover the speaker. Cover the ENTIRE surface of the chassis that will reside underneath the cut-out of the box. What we're doing here is trying to dampen any highly-reflective surface to keep any high freqs that escape beyond the filters from bouncing around and reflecting / phase shifting things.

So play around with box size, layers of filtering, etc to your liking. I knew that this would cut down on the high frequencies, but I didn't realize the depth of sound it provides - very pleasant for kitchen products. :)
 

altair

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question receiver taget and lowe

hi Herzian , what are the differences between the target receiver hf3 / P and lowe hf150 ?,
what do you recommend for the purchase?

thanks
antonio
 

nanZor

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The HF150 for sure - if you can find one of these radios in good condition. Just be aware that they are "vintage" material, so you may want to be good on your repair skills if you are thinking about making this a daily driver.

The Targer receiver was intended for much the same audience - European listeners dealing with huge signals that tend to overload receivers - even much better ones were affected.

But, back in the day, the HF150 was in a higher stratosphere price wise. So the Target was a stripped down version to make nearly the same affordable.

They are both not *really* ideal for beginner swl's, despite their simplistic operations. The lower sensitivities of about 0.5uv for HF, and with the Targets further decline above 13 mhz (on purpose for the desired market) makes an external preamp, and perhaps a passband filter highly desirable in other areas of the world.

In fact, a full blown set of accessories for the HF150 was like this when you wanted to take it to the next level. With my Target, I just use a little MFJ preamp / tuner combo which gets the job done. If one really knew what they were doing they could specialize with antennas customized for their purpose, but generally the preamp / filter was the easiest way to upgrade.

My Target, even though I paid more than I should, was done primarily to have fun, and enjoy some of the glory days of British swl engineering. Although not Racal performance, many British receivers were simply amazing.
 

AlphaFive

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Target HF3

I was looking at the Target HF3 on the NASA website, they do offer a vertical antenna to match the unit. Any experience using the NASA vertical antenna with the HF3? Is it practical, or would a much better investment be to go ahead and utilize some type of loop with the HF3? I am interested in the Target unit, but the antenna question with it has put me off.
What I mean by that is I observed the HF3 does not have a standard BNC connection on the rear. I would have to concern myself with finding a proper adapter to mate with the connection on my coax. It has so far made me look elsewhere.
 
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nanZor

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I have no experience with the NASA amplified antenna so I can't comment other than it gets its power from the Target rx.

The rca antenna connection needs to be handled with care if you are going to use an adapter - do NOT twist it, just push in or pull straight out with and adapter, or you'll twist the center internal connection off the board. Easy repair, but still.

The Target, especially if imported, may not represent the best price / performance ratio for someone who doesn't really know why they want such a retro-design in the first place. It's kind of a nice thing, but yeah it will work.

Without denigrating NASA, or their main marketing demographic - light duty European mariners that would like a listen now and then to AM/SW broadcasts, or perhaps marine ssb notifications, with a speaker loud enough to overcome cabin/engine noise easily, and not kill the starter battery with a piddling amount of receive current - I'd recommend something else.

Maybe the Alinco DX-R8T receiver would be more fitting for you - unless your heart is totally set on the Target. Heh, get them both like I did for different reasons!

Don't rush into it - if the antenna jack format is going to be a deal breaker - take even more time. :)
 
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