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Author Topic: General Coverage Comms rxer down to 20KHz?  (Read 1272 times)

Offline Looking-Glass

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General Coverage Comms rxer down to 20KHz?
« on: December 09, 2018, 0927 UTC »
Does any one know of a HF gen coverage receiver or amateur transceiver that goes as low as 20KHz or even 10KHz would be even better?

Preferably something recent/modern.

All my gear cuts out at 30KHz...except for the FT-2000D where I use the 10KHz receive clarifier to get down to 20KHz... ;)
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline Josh

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #1 on: December 09, 2018, 2009 UTC »
As I recall, the R71 will go down to 10KHz either by tricking the tuner, or using one of the replacement rom boards. A selective voltmeter might be a easier piece of gear to get that tunes down there without funky programming or replacing roms.
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Offline pnoelw

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #2 on: December 10, 2018, 1434 UTC »
The AOR AR7030 goes all the way down to well below 10kHz.

Noel.

Offline Josh

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #3 on: December 10, 2018, 2110 UTC »
It's said that the lower you can tune your rig is directly proportional how well the engineers regarded the cleanliness of their local oscillator.
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Offline n3ckf

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #4 on: December 11, 2018, 0540 UTC »
I think the RX-340 goes down that far.  Mine seems to anyway. 
Tentec RX-340, Icom IC-7600 w/G5RVMax antenna
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Offline ThElectriCat

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #5 on: December 11, 2018, 2353 UTC »
As far as radios that are not insanely expensive/hard to get. The Rycom 6040 selective voltmeter is a good choice. I think it goes down to less than 10 Kc, and up to a few Mc. it has a frequency counter as the freq. display, and digital automatic frequency control,  so its about as stable as a synthesized rig and as easy to read. they turn up on eBay fairly often for between $200 and $1000. Of course, earlier models without a digital readout can often be cheaper. I used to have a Rycom 3121A, which had a dial rather than a readout. My first NDB was heard with that radio.
In another life, I could have been a telephone engineer.

Offline ThaDood

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #6 on: December 12, 2018, 1733 UTC »
My Kenwood TS-2000X will dial down there as well. It initially stops at 30kHz, but the RX RIT can dial down an addition -20kHz so that you can end up at 10kHz. If this rig does this, then I suspect that the TS-590, TS-480, TS-570, TS-990, and other Kenwood rigs could probably do this too, and no modifications required.
From DC to light, I take a huge spectrum bite!

Offline ThElectriCat

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #7 on: December 12, 2018, 1832 UTC »
I also Forgot to mention Demodulators. These can be hard to find unless you search them specifically, because 'Radio' often is not in the title. The receiver I use is a WJ DMS-105a-2 Watkins Johnson demodulator. You probably won't find one of those, but there are others. Being designed for subcarrier listening on microwave baseband channels, many are not very sensitive, and need an external preamp, but they pretty much all will tune as low as 4 kilocycles, as this is the first channel in an FDM telephone cable. Mine (and many others) will tune to 1000 Hz or even slightly lower. Modern amenities are not to hard to find either as many demodulators are either digitally controlled, or fully software defined.

P.S, if you want to use a computer for the low end stuff, there is no better source of info than this site,
http://www.vlf.it/
In another life, I could have been a telephone engineer.

Offline Stretchyman

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #8 on: December 12, 2018, 2123 UTC »
Most interesting!

Str.
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                            Buy one from me, NOW!

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Offline Josh

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #9 on: December 13, 2018, 2247 UTC »
I also Forgot to mention Demodulators. These can be hard to find unless you search them specifically, because 'Radio' often is not in the title. The receiver I use is a WJ DMS-105a-2 Watkins Johnson demodulator. You probably won't find one of those, but there are others. Being designed for subcarrier listening on microwave baseband channels, many are not very sensitive, and need an external preamp, but they pretty much all will tune as low as 4 kilocycles, as this is the first channel in an FDM telephone cable. Mine (and many others) will tune to 1000 Hz or even slightly lower. Modern amenities are not to hard to find either as many demodulators are either digitally controlled, or fully software defined.

P.S, if you want to use a computer for the low end stuff, there is no better source of info than this site,
http://www.vlf.it/

Oops, forgot our pc's have soundcards that can listen down there, just need an antenna, some software, and you're all set.
http://www.vlf.it/pernter1/x-fi_modifications.html
Conveniently located near Vincennes Indiana.

Offline Looking-Glass

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #10 on: December 18, 2018, 0733 UTC »
The FT-2000D base radio goes down as far as 20KHz with the introduction of the Receiver Clarifier, however, I also notice with the big Yaesu that receiver sensitivity also drops dramatically below 40KHz, unlike the small Icom IC R-75 which holds it's own.

Will look at the AOR AR7030 when I have time over the weekend, thanks for that, also will look and see what a RX-340 is too...thank you people.
Hermitage Flat, NSW.

Grid Square:  QF56dm.

Yaesu FT-2000D, ICOM IC-736 HF/50MHz, ICOM IC R75 & Tecsun S-2000 to 450 feet of wire, and a multi band vertical of dubious reliability.

Offline ThElectriCat

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #11 on: December 18, 2018, 1705 UTC »
If you use an active antenna or antenna preamplifier the low sensitivity may not be a problem, many such receivers just have a 6dB/octave roloff below a certain frequency, or a transformer that is designed to be lossy at lower frequencies to prevent overloading from static or broadcasts. the performance and selectivity should not suffer as long as you can get enough signal into the receiver.

There are also modifications listed online for many rigs, and improving LF performance may be as simple as removing an RC circuit or winding a new transformer, I however, understand if you would want to modify n expensive new radio. not so sure I would either.

(I have this problem, where I modify things that work perfectly and break them, most of my repair skills came from repairing stuff I broke)
In another life, I could have been a telephone engineer.

Offline Josh

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #12 on: December 18, 2018, 2131 UTC »
Also, possibly someone still makes converters that shift the vlf up to say 10MHz or wherever. These might offer improved performance as they're designed for the band in question but transvert the sigs where a hf receiver will be at peak performance.
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Re: General Coverage Comms rxer down to 20KHz?
« Reply #13 on: December 27, 2018, 0001 UTC »
My WJ 8718 will tune down to 5khz  I think the Racal will too
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Offline ThElectriCat

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Re: General Coverage Comms rxer down to 20KHz?
« Reply #14 on: December 28, 2018, 1713 UTC »
The wj8718, 8716 and 8718-a don't all say they will go that low, but they probably will.  My 8718 specifies 500 KHz as the bottom end, but will tune down to 15 or so
In another life, I could have been a telephone engineer.