QRMs and Professional Rack-mounted HF Receivers vs. Hobby Grade Ones

yahya

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I am interested in your experiences in combating QRMs, especially in agglomerations and how the selection of receivers and ancillaries helped to mitigate that problem. How would you compare older professional-grade 19" rack-mounted HF receivers used with preselectors to what is currently available on the marked as moderately priced equipment addressed to HAMs and enthusiasts, including SDR receivers?

I always thought that the professional rack-mounted HF receivers outclassed in most cases the cheaper but contemporary rig addressed to the amateur market. Since the QRMs became a serious problem to many SWL and HAMs in big cities in the recent decades, I wonder if looking for such a professional 19" receiver with and an external preselector is worth the cost considering the possibility of equipment failure due to the aging. Collins, Harris and many other 'big radio' companies made professional external preselectors, both manual and, later, controlled from the receiver.

What in your opinion would be a match to such a 'professional' 19" set from the contemporary array of amateur market products available today?
 

merlin

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It is very hard, even with the high end rack and Mil receivers. Where those are employed, most have extreme antennas like the full HF log periodic 100 foot up or the T3FD at 80 foot, possibly even full wave Rhombic. These pull in even the weakest of signals, enough to get a decent signal to noise ratio.
When you say 'outlast', there are 50 year old tube radios, like the Hammerlund and R390-URR still being used.
My main SWL receiver is my Kenwood TS-440S, bought used in 1981. It sits here now, listening for a SW station in Germany.
Wish I still had my R390 and FRT-24D
Maybe look into some of the better AOR receivers.
 

yahya

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Thanks for the reply. Right, I supposed that the rack receivers were used predominantly with serious antennas installed on large antenna farms.

I wonder how the modern commercial-grade SDR receivers compare to the older rack ones as I had no experience with either. If I'm not mistaken, eg. Elad made external preselectors for their SDR receivers. Are such combos as efficient as professional/mil grade rig?
 

Token

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I am interested in your experiences in combating QRMs, especially in agglomerations and how the selection of receivers and ancillaries helped to mitigate that problem. How would you compare older professional-grade 19" rack-mounted HF receivers used with preselectors to what is currently available on the marked as moderately priced equipment addressed to HAMs and enthusiasts, including SDR receivers?

I always thought that the professional rack-mounted HF receivers outclassed in most cases the cheaper but contemporary rig addressed to the amateur market. Since the QRMs became a serious problem to many SWL and HAMs in big cities in the recent decades, I wonder if looking for such a professional 19" receiver with and an external preselector is worth the cost considering the possibility of equipment failure due to the aging. Collins, Harris and many other 'big radio' companies made professional external preselectors, both manual and, later, controlled from the receiver.

What in your opinion would be a match to such a 'professional' 19" set from the contemporary array of amateur market products available today?

You are really going to have to define what you mean by "professional 19" rack mounted receivers.

But when discussing specifically QRM there is little in the way of "pro" gear that works better than (or often as good as) a modern, or semi-modern, ham contest rig. Starting in time with something similar to the FT-1000D and after, they simply handle QRM very well. Most of the ham contest rigs made in the last 25+ years are truly excellent in a heavy QRM environment.

T!
 

yahya

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Thanks for the follow up. It's interesting what you wrote about the HAM contest rig.

What's your take on external preselectors used with the mid-range receivers. Do you have any recommendations?
 

mayidunk

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If you can find a used ICOM IC-R75 with the DSP module installed in it, you'll have a very nice HF communications receiver that'll do quite well at mitigating QRM. As well, an older analog HAM transceiver might also do the trick. A lot of the newer HAM transceivers are SDRs with standard controls on them, along with pretty efffective digital tools for battling QRM. I believe there are still a few new analog transceivers being sold as well, which also have digital noise abatement tools. I have an old analog Yaesu FT-1000D that I use as a SW receiver. While it doesn't have all the bells and whistles that newer tranceivers have, it still does a decent job at keeping the QRM at bay.

Just a reminder, while you do not need to have a HAM radio license to purchase HAM transceivers, you will need one to transmit with them. Without a proper license, you are absolutely not allowed to transmit with them for any reason, on any frequency, at any time! Not in an emergency, not even to test them! For you, and I, they are receivers only.

That being said, while the tabletop communications receivers of yore may be getting long in the tooth, HAM transceivers can still give you as good, if not better, performance as those fabled, high end radios.

Good luck!
 
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mayidunk

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Thanks for the follow up. It's interesting what you wrote about the HAM contest rig.

What's your take on external preselectors used with the mid-range receivers. Do you have any recommendations?
I still use an old Grove MINITUNER tun3 preselector. It's good for peaking frequencies that you're listening to, but doesn't really act to filter out signals adjacent to the one you want to hear. However, a good receiver will have good IF filters, and some of the higher end units will also have roofing filters on them as well.

MFJ used to sell a couple of desktop active antennas back in the day that could also be used as preselectors for external antennas. They also sold passive preselectors. Palstar sold a desktop active antenna that you could use as a preselector for an external antenna. AMECO sold one as well, though I don't remember if it could be used with an external antenna. Passive preselectors, like my MINITUNER tun3, work just as well, and don't need batteries or wall warts. If you search for preselectors on ebay, you'll probably find a few out there.

Just one more thing, be aware that the higher up in frequency you tune, the less effective preselectors tend to be. That doesn't mean they're worthless at higher freqs, it's just means their performance tends to be less pronounced as at the lower freqs.
 
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yahya

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Thank you very much indeed for the detailed reply. Now, I understand that either an IC-R75 with DSP, or a second hand contest HAM radio (which are pricey, alas) should solve the issue with QRMs.

Since I have no experience with the professional grade rack-mounted receivers and the associated preselectors, my understanding is that what is available to hobbyists, like the TUN-3 that you mentioned, may be heavily constrained. While Palstar makes decent quality products, I cannot say so about MFJ's. I presume that the 'professional' grade preselectors may have been more efficient, eg. Collins HF-8060 and Harris RF-507 or RF-551 compared to what is available on the hobbyist market. Obviously, these professional preselectors mostly aimed at stunning strong interference in physical vicinity of the receivers, eg. to enable full duplex on HF from within a communications central.

By the way, there is a small USB-powered Airspy HF+ Discovery receiver on the market, which apparently has embedded preselectors. It's size is a bit surprising. If someone has experience with both this receiver and the professional rack-mounted ones, please share the experience on their performance especially in the QRM environment.
 

merlin

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Thanks for the follow up. It's interesting what you wrote about the HAM contest rig.

What's your take on external preselectors used with the mid-range receivers. Do you have any recommendations?
My Watkins Johnson had a preselector, separate, stand alone, it will work with any HF receiever with an antenna connector.
What was nice was the tunable bandpass filter, you could rid a lot of noise before ever getting to the receiver.
 

merlin

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there is a small USB-powered Airspy HF+ Discovery receiver on the market, which apparently has embedded preselectors. It's size is a bit surprising. If someone has experience with both this receiver and the professional rack-mounted ones, please share the experience on their performance especially in the QRM environment.
The preselectors are OK but you just can't escape the noise, It is a worth while SDR but will never match any quality receiever.
A preselector would do it justice, I only have an FM BC trap on mine.
 

merlin

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Elad made external preselectors for their SDR receivers. Are such combos as efficient as professional/mil grade rig?
They will never compare to high end MIL grade receivers. Again, comparing apples to oranges.
 

yahya

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My Watkins Johnson had a preselector, separate, stand alone, it will work with any HF receiever with an antenna connector.
What was nice was the tunable bandpass filter, you could rid a lot of noise before ever getting to the receiver.

Could you please share the nomenclature of that stand alone preselector?
 

dlwtrunked

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Thank you very much indeed for the detailed reply. Now, I understand that either an IC-R75 with DSP, or a second hand contest HAM radio (which are pricey, alas) should solve the issue with QRMs.

Since I have no experience with the professional grade rack-mounted receivers and the associated preselectors, my understanding is that what is available to hobbyists, like the TUN-3 that you mentioned, may be heavily constrained. While Palstar makes decent quality products, I cannot say so about MFJ's. I presume that the 'professional' grade preselectors may have been more efficient, eg. Collins HF-8060 and Harris RF-507 or RF-551 compared to what is available on the hobbyist market. Obviously, these professional preselectors mostly aimed at stunning strong interference in physical vicinity of the receivers, eg. to enable full duplex on HF from within a communications central.

By the way, there is a small USB-powered Airspy HF+ Discovery receiver on the market, which apparently has embedded preselectors. It's size is a bit surprising. If someone has experience with both this receiver and the professional rack-mounted ones, please share the experience on their performance especially in the QRM environment.
Your "by the way" made me laugh. I have a AirSpy HF+ Discovery($170), an ICOM R9500 receiver ($13,000), an ICOM IC-R8600($2500), various SDRPlay. I am using one of the HF+ Discovery right now and do not know when I last turned the others on. That tells you what I think. And the World Radio Television Handbook (WRT) rates them (Overall)
AirSpy HF+ Discovery *****
ICOM IC-R9500 *****
ICOM IC-R8600 ****

To be truthful, unless one has and AirSpy HF+ Discovery to compare, I cannot really take them serious when they talk about HF receivers and how good they are. If you are serious about HF and have a PC/labtop, spend the $170 to get an HF+ Discovery. If you want VHF/UHF also get an AirSpy R2. If you are short on money and cannot afford both bands this way, get a SDRPlay.
 

yahya

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Great information! Thank you very much indeed for sharing. That's what I was looking for.

May I just ask you, while using the AirSpy HF+ Discovery, did you experience any problems related to the quality of reception and affecting receiver's behavior, which could originate eg. from nearby transmitters, like a HAM pumping 1kW on HF bands just a block away from you, unless you live in a 'transmitter-free' area?
 

jazzboypro

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Your "by the way" made me laugh. I have a AirSpy HF+ Discovery($170), an ICOM R9500 receiver ($13,000), an ICOM IC-R8600($2500), various SDRPlay. I am using one of the HF+ Discovery right now and do not know when I last turned the others on. That tells you what I think. And the World Radio Television Handbook (WRT) rates them (Overall)
AirSpy HF+ Discovery *****
ICOM IC-R9500 *****
ICOM IC-R8600 ****

To be truthful, unless one has and AirSpy HF+ Discovery to compare, I cannot really take them serious when they talk about HF receivers and how good they are. If you are serious about HF and have a PC/labtop, spend the $170 to get an HF+ Discovery. If you want VHF/UHF also get an AirSpy R2. If you are short on money and cannot afford both bands this way, get a SDRPlay.

I have the Airspy HF+ Discovery, SDRPlay duo, R30 and R8600. Maybe i'm doing something wrong but the HF+ does not hear anything more or better than the other radios.
 

dlwtrunked

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I have the Airspy HF+ Discovery, SDRPlay duo, R30 and R8600. Maybe i'm doing something wrong but the HF+ does not hear anything more or better than the other radios.
You have likely never given it a really challenge like a very weak station next to a very strong one and then use all the features. For many listeners and what they do, your experience might be typical. Or compare the HF+ to any of the others using a YouLoop antenna (not the cheaper Chinese copy), one quickly sees the sensitivity difference. You can only compare using something hard to receive. I would expect the 8600 and duo to do well but my tests have the HF+ doing better. The dou should be better than the 8600 in dynamic range and I would give it 2nd place. The R8600 of curse does not need a PC but is a step down (yes, I know some will argue). I back shelved the R30 simply because I could always grab one of my 4 HF+ Discovery (or Airspy R2 for VHF/UHF) and do better.
 

mayidunk

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Thank you very much indeed for the detailed reply. Now, I understand that either an IC-R75 with DSP, or a second hand contest HAM radio (which are pricey, alas) should solve the issue with QRMs.

Since I have no experience with the professional grade rack-mounted receivers and the associated preselectors, my understanding is that what is available to hobbyists, like the TUN-3 that you mentioned, may be heavily constrained. While Palstar makes decent quality products, I cannot say so about MFJ's. I presume that the 'professional' grade preselectors may have been more efficient, eg. Collins HF-8060 and Harris RF-507 or RF-551 compared to what is available on the hobbyist market. Obviously, these professional preselectors mostly aimed at stunning strong interference in physical vicinity of the receivers, eg. to enable full duplex on HF from within a communications central.

By the way, there is a small USB-powered Airspy HF+ Discovery receiver on the market, which apparently has embedded preselectors. It's size is a bit surprising. If someone has experience with both this receiver and the professional rack-mounted ones, please share the experience on their performance especially in the QRM environment.
I have had several MFJ products over the years, and they have performed rather well in my opinion. That's why they were also known as "Mighty Fine Junk!" I'm currently using an MFJ-616 Speech Intelligibilty Enhancer that is basically a four band audio equalizer. However, it's more than a mere EQ, it's tuning ranges are specifically designed to accentuate the vocal range, and it not only attenuates audio within the four band ranges, but also amplifies them as well. It really is an effective tool for ferreting out hard to hear signals. It's made with very high quality components, and is built like a brick shi... well, you know. It's over 30 years old, and it looks, and performs like it was brand new. Not a scratchey potentiometer or intermittent switch to be found!

The tun3 definitely makes a difference as it does increase the S/N, though I doubt it's anywhere near as effective as the preselectors you've mentioned. I certainly wouldn't expect it to block any nearby transmissions at, or near the frequency I'm tuned to.

Also, while the Icom radio with the DSP module will help to reduce, and sometimes, eliminate QRM, there really is no "silver bullet" that will eliminate all QRM, all the time! Noise will always be a constant battle, unfortunately. I also have an old JPS NIR-12 Noise and Interference Reducer. It has dual DSPs in it, and while it can sometimes produce essentially noise free, easy to hear signals, it doesn't happen all that often! In reality, it's often a compromise between noise and intelligibility, leaving you to experiment with different settings in order to make out what people are saying, while still having to put up with all that noise!
 
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jazzboypro

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You have likely never given it a really challenge like a very weak station next to a very strong one and then use all the features. For many listeners and what they do, your experience might be typical. Or compare the HF+ to any of the others using a YouLoop antenna (not the cheaper Chinese copy), one quickly sees the sensitivity difference. You can only compare using something hard to receive. I would expect the 8600 and duo to do well but my tests have the HF+ doing better. The dou should be better than the 8600 in dynamic range and I would give it 2nd place. The R8600 of curse does not need a PC but is a step down (yes, I know some will argue). I back shelved the R30 simply because I could always grab one of my 4 HF+ Discovery (or Airspy R2 for VHF/UHF) and do better.

Thanks for the info. I used to have the youloop antenna but it broke after a few days and i replaced it with a W6LVP loop. I will try again just for fun. Might be location dependent also. Maybe the HF+ works better with the youloop than with the W6LVP loop.
 

mayidunk

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The Radio Society of Great Britain (RSGB) has published a book, "EMC & RFI Know How", edited by Steve Telenius-Lowe. Apparently (I haven't read this yet...) he has compiled information from many sources around the world on how they have battled QRM. Quoting from the description on their online shop:

"This book has drawn on expertise from across the world and includes material from the UK, USA, Germany, Greece and the Netherlands. You will find sections dedicated to sources of interference such as Lighting, xDSL, Renewable Energy, Air Conditioners, Air Source Heat Pumps, Power Line Noise and Power Supplies & Chargers. EMC & RFI Know How also takes the reader through practical ways of defeating the problem of interference. Home constructors are well catered for with the circuit of an HF receiver suitable for directionfinding, a preselector to eliminate interference from powerful broadcast stations, filters to stop breakthrough to TVs, and even a ‘QRM-Eliminating’ antenna. Advice is also given too on how to prevent breakthrough from amateur transmissions spoiling the family’s enjoyment of television programmes!"

If you're having issues with relentless QRM ruining your day, or a nearby amateur station or broadcast radio station swamping your receivers, this might help. DX Engineering is selling this book for around $24, but the RSGB online shop is selling it as a special offer at a price of 9.99 GBP, including VAT at 0%. Here's the link:


Amazon is also offering it as a Kindle book for 15.99 GBP. I'm not sure about VAT. Their link for this book is:


Note to Moderators: If I've crossed any lines with this post, please feel free to remove it. I only do this because finding something that pulls information on this subject into one place can be a big help for people. Please note that I receive no compensation from anyone for sharing this.

Hope this helps!
 
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