Low Pass Filter For SWL?

[hfflunki]

im cheap and broke most of the time but i use a graghic eq that you usualy get for 10-30 dolars used at ane used electronics store or garage sale they do basicly the same as a audio fillter of any kind by the way wolverine radio is sighning off wriwith there sstv signal right now if anyone cares

thanks dan

 

[brandon]

Those noise cancelers like the ANC-4 and MFJ-1026 do amazing things.

 

[prcguy]

I would not expect the low pass filter to make any noticeable difference but maybe you are line of sight to Sutro tower and something in the VHF/UHF band is causing some problems.

I say return the filter just because of the basic lack of salesman knowledge and I have several spares and would send you one.
prcguy

Thanks for the advise zz I have seen that one and may look into it-HRO boss suggested it too.
Sorry Warren-but the hope in this is that Mark the manager there is a longtime ham and is of your school-he has to hold everything together there. The young man I dealt with needs more training and a breifing on not being snarky. Mark is taking care of me by accepting the return and maybe pointing me to an ANC-4 or a preselector.
This filter is helping ssb and a small portion of AM hiss-there must be something affecting me on HF here above the Bencher's rolloff. So it isn't a total loss-without the filter inline, the AM hiss I get on signal fade is pretty harsh-with the filter it's sort of softer lol. Just that tiny improvement makes me almost not want to return it.

 

[ridgescan]

im cheap and broke most of the time but i use a graghic eq that you usualy get for 10-30 dolars used at ane used electronics store or garage sale they do basicly the same as a audio fillter of any kind by the way wolverine radio is sighning off wriwith there sstv signal right now if anyone cares

thanks dan

I agree Dan I have my R75 at the bedside running through my old faithful Sony STR-D790 (A/V receiver) with a built-in EQ that comes in mighty handy

Those noise cancelers like the ANC-4 and MFJ-1026 do amazing things.

I'll check that MFJ too B thanks

I would not expect the low pass filter to make any noticeable difference but maybe you are line of sight to Sutro tower and something in the VHF/UHF band is causing some problems.

I say return the filter just because of the basic lack of salesman knowledge and I have several spares and would send you one.
prcguy

Thanks prcguy it's going back and my girl says I should make them pay gas&bridge fare as well

 

[nanZor]

prcguy - you have been ordered to keep us updated on the KX3! I'm extremely interested in the current consumption since I'm solar as a side hobby. AA's would blow my mind for reception only.

ridgescan - The R75 filter for am might be a bit wide. Have you tried ECSSB mode for AM? (Purposely use ssb for am reception - just tune it in accurately and slowly (VBT set in the middle too) to either the upper or lower sideband. Give it a shot and see what you think. The R75 has the slow resolution to be able to do this as you zero-beat the carrier out of existence.

 

[mondomusique]

I recently got a used RF-Systems P-3 Preselector for use with my SDR. It works as advertised, I can see it attenuating out of band signals on the SDR waterfall display. That said, it really makes no difference as my radio is not suffering overload from any out of band signals, there are no flamethrowers near me. Though it's fun to have a few knobs to raise the Q of a signal when playing SDR, in my case it makes no difference to the radio.

As we all know, antenna and radio are the big pieces of the puzzle, additional add-ons rarely make much impact beyond that.

If I was you Ridgescan, as an experiment I would construct a homemade magnetic loop antenna for a favorite frequency just to see if it changes the sound of signals reception. Do some internet research for construction tips and get an air variable capacitor on Ebay, it should be an inexpensive project. Supposedly a magnetic loop works great in urban environments (relatively quiet noise floor).

So my experience was, preselector, kinda useless in my situation.

 

[ridgescan]

ridgescan - The R75 filter for am might be a bit wide. Have you tried ECSSB mode for AM? (Purposely use ssb for am reception - just tune it in accurately and slowly (VBT set in the middle too) to either the upper or lower sideband. Give it a shot and see what you think. The R75 has the slow resolution to be able to do this as you zero-beat the carrier out of existence.

Thanks for the tip hertzian. I have also found in my using the r75 that it can improve and stabilize AM signals as well as weaker ssb by just running the RF gain back enough to cover fade, because the annoying hiss happens in the fade. Not to mention the several filter options on top of several noise reduction settings that radio has you could hone for days. I was just looking impulsively for a filter if they happened to have one since I was there. My reception here is actually really good due to good RF grounding, but as any mad tinkerer, I'm always open for more improvements on noise. I could simply blow a big wad on a Wellbrook and SDR, throw my rigs in the closet and call it a day, but prefer to work with what I have as part of the fun of the hobby

I recently got a used RF-Systems P-3 Preselector for use with my SDR. It works as advertised, I can see it attenuating out of band signals on the SDR waterfall display. That said, it really makes no difference as my radio is not suffering overload from any out of band signals, there are no flamethrowers near me. Though it's fun to have a few knobs to raise the Q of a signal when playing SDR, in my case it makes no difference to the radio.

As we all know, antenna and radio are the big pieces of the puzzle, additional add-ons rarely make much impact beyond that.

If I was you Ridgescan, as an experiment I would construct a homemade magnetic loop antenna for a favorite frequency just to see if it changes the sound of signals reception. Do some internet research for construction tips and get an air variable capacitor on Ebay, it should be an inexpensive project. Supposedly a magnetic loop works great in urban environments (relatively quiet noise floor).

So my experience was, preselector, kinda useless in my situation.

Good info mondo-thanks

 

[prcguy]

I use SSB for AM SW reception because it lessens or completely removes the annoying fade. You can then reduce some RF gain to quiet the receiver and balance that setting with the worst fade for very comfortable listening.

My K3 has synchronous AM detection which chooses one sideband and auto tracks the carrier, which is a dream for SW or any HF AM reception.
prcguy

Thanks for the tip hertzian. I have also found in my using the r75 that it can improve and stabilize AM signals as well as weaker ssb by just running the RF gain back enough to cover fade, because the annoying hiss happens in the fade. Not to mention the several filter options on top of several noise reduction settings that radio has you could hone for days. I was just looking impulsively for a filter if they happened to have one since I was there. My reception here is actually really good due to good RF grounding, but as any mad tinkerer, I'm always open for more improvements on noise. I could simply blow a big wad on a Wellbrook and SDR, throw my rigs in the closet and call it a day, but prefer to work with what I have as part of the fun of the hobby


Good info mondo-thanks

 

[E-Man]

prcguy - you have been ordered to keep us updated on the KX3!

+1 very interested in receive comparisons between the K3 and Kx3.

Thanks

 

[prcguy]

There are a lot of comparisons online already. Basically the KX3 beats every receiver tested in close spaced dynamic range and other things that will make it survive in contest type situations and it rates better than the K3, the $11k Icom 7800 and everything else.

You have to keep in mind its a small portable rig and the speaker is tiny and its only 10w, so it would need some support equipment to compete with the larger rigs for comfort and output power.
prcguy

+1 very interested in receive comparisons between the K3 and Kx3.

Thanks

 

[nanZor]

I could simply blow a big wad on a Wellbrook and SDR, throw my rigs in the closet and call it a day, but prefer to work with what I have as part of the fun of the hobby

How about a quickie substitute with a coax loop. Here is one example:

G1ZRN's Loop antenna

Thing is, if your feedline is short, say no more than about 20 feet, you may be able to skip the usual tuning capacitor, and merely activate the 2nd preamp in the R75! It's not perfect as the 2nd preamp is intended mainly for the higher frequencies, but at least you don't have to run outside or up on the roof to tune the thing. Just keep the total circumference of the loop at or below 1/10th wavelength for the highest frequency you want to go.

Since we're looking for the best S/N, and not overall signal strength, the -12 to -16db difference may be tolerable. It really sounds worse than it is. So without the tuning capacitor you compensate a little with the R75's additional preamp. Then, if you still don't want to go outside, a T-type tuner at the rig will help even further.

Obviously the real way to do it is to put some sort of amp between the loop and the feedline. BUT, if you've got some hunks of coax laying around (impedance of the coax loop doesn't matter much - we're not even trying to make a match), and no more than about 20 feet of feedline (longer than this and the t-type tuner will have problems), you CAN enjoy the properties of a nifty homebrew loop sans remote tuning.

I got my taste for loops this way when I cobbled it together many many years ago, and just wanted to see what it was about without making a remote tuning / matching network, and just keep it all at the rig initially.

Something to play with anyway to get a taste..

 

[ridgescan]

Looks like it could be fun H-thanks for posting it

 

[majoco]

Ridgy's original post said:

I asked the guy there if they made a filter to improve hiss on weaker HF signals

So where is the hiss coming from? External or internal? My Kenwood R2000 had a load of front-end hiss until I fitted a mod to give me an RF gain control.
If you disconnect your antenna, how much hiss is left if you wind the RF gain up full? If you now reconnect the antenna with no signal, how much noise/hiss do you have?
If you back off the RF gain you may be surprised to find that the internally generated hiss is greatly reduced but without losing much or any sensitivity.
Does the R75 allow you to select narrow/wide filters - a narrower filter will reduce the hiss - you may have to do a mod so that the SSB filter is in circuit all the time.!
Do you use the pre-amp? I have used an external pre-amp and found that it's performance minimal to say the least. It sounded like it was doing good, but in fact the additional noise only masked weak signals!

Some interesting stuff here...

http://n9ewo.angelfire.com/icr75.html


Have fun!

 

[ridgescan]

Thanks Martin don't get me wrong here-my reception is great, the RF grounding I did is very effective and now has things to the point where that hiss you get when a distant signal fades out/in on the r71a is something I wanted to perfect upon, but it's not a signal killer by any means.
BTW at the risk of embarrassing you yet again, I finally tried something you suggested to me a while back and it works really well-I ran a vertical 40' leg of rg59u connected to my PAR's ground lug down to an electrical service groundpoint near the earth going underground under the building. There I have both the center lead and shieldbraid connected together to that ground. Up at the PAR, only the center lead is connected. I was receiving ABC central Australia on I think 4930kHz at +10 and 50,000 watts in short, thanks to your advise I enjoy some powerful reception here. So thanks to you and the ship radioman experience you share here Martin!
Will dive into that link later

 

[BDM123]

While this does not address all noise issues mentioned. I find using many techniques together help eliminate noise or keep it at least low. Common mode chokes are always a good thing when properly used.

http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf

Common-mode chokes


-Brian

 

[ridgescan]

While this does not address all noise issues mentioned. I find using many techniques together help eliminate noise or keep it at least low. Common mode chokes are always a good thing when properly used.

http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf

Common-mode chokes


-Brian

Good info BDM thanks for posting it
I totally agree with the bolded part of your post-my bastardized antenna system here is the result of much trial/error..a ton of trips to the roof!