Frequency Selective Voltmeters as Receivers

[spongella]

Saw a comment on this forum about frequency selective voltmeters, did some data mining on the 'Net and it appears these were old commercially-manufactured units used by power companies. Perhaps there are some folks on this forum who used these on the job.

Anyway, some of these units cover LF, MW, and some even cover up to 9 megs AM/SSB. Given, they're not designed for LF/MW/SW hobbyists but wondering how they would fare as LF/MW receivers. I'd imagine these must have cost a fortune back in the olden days.

Thanks for any comments.

 

[zz0468]

They're basically precision calibrated SSB receivers. Frequency coverage is from 0 to anywhere up to 30 MHz depending on the make and model. They can make excellent VLF receivers, but typically don't have amenities like noise blankers. They were used to set levels on analog FDM mux.

I would expect a preamp to be necessary. The receive threshold is somewhere around -70 dbm.

I paid about $10k a piece back in the 80's.

 

[k7ng]

Selective voltmeters...

The HP 3586 series are awesome units; I recommend the 3586C if you're going to go looking for one. They measure frequency to fractional Hz, levels to fractional dB, and actually provide an RF output exactly what is displayed on the receive frequency window. VLF to above the top end of HF. About 90 pounds of 1980's technology.

No AM reception except by zero-beating the AM carrier in SSB mode, and there isn't a big variety of filter bandwidths. I don't find it a big deal, I'm not looking for high fidelity. They aren't a general-coverage receiver but have many uses for off-air evaluation of signals.

 

[majoco]

I bought an HP3586A in a not-fully-operational mode for a pittance and fortunately found the major fault quite quickly - someone had replaced a screw for the handle that was far too long which bit into the front panel printed circuit board shorting one of the 5volt supply rails to ground which overloaded and overheated the power supply - fortunately it survived! Other minor things were easily dealt with and now I have a magic piece of gear that I use for all sorts of things. The audio output on the rear panel is very good, filters are good of course and the frequency accuracy and stability are excellent. It will lock on to any carrier above a couple of microvolts and show its frequency down to 0.1Hz! - and as a bonus will radiate a carrier to the same accuracy! You'll have to get your head around working with dBm's instead of uV - mine goes down to -120dBm which is around 0.25uV in 50 ohms. It's an engineering marvel inside too - the 2-volume manual is online and a couple of guides to get you started. Here's mine displaying our local AM band station....

 

[mmckenna]

I picked up a Rycom unit off e-bay a year or so ago.
Battery powered, runs off an internal 12 volt rechargeable battery. I replaced that with a new one.
Weighs about 7 pounds.

Receiver works well. I haven't felt the need for a preamp, but it would be interesting to try.

The Rycom is a basic unit, designed for field portability.

I think I paid $45 - 50 bucks for mine. Put a new $20 12 volt battery in it, charged it up, cleaned the case and it works fine.

I built a loop antenna with PVC pipe and that seems to be a good combination. Picked up Aero/NDB long wave beacons fairly well. Pulled in a few DX AM stations, well, too. Issue though, at least with mine, is the IF width is not ideal for AM listening. In other words, not a radio you are going to want to listen to music on, but great as a receiver for chasing down signals.

There's usually a few on e-Bay at any given time. I think mine had a calibration sticker on it from the mid 1990's.

 

[northzone]

I had both a Sierra and a Rycom for my work with analog microwave. The indivual channel cards actually modulated SSB. Then groups of channels were mixed together to modulate the microwave baseband (70 mhz) with an FM signal.

We once put in a system that had 90 voting receivers with constant status tone. This caused the baseband to go into a Bessel Null and we lost all baseband.

Fun stuff.

 

[jimvm]

Frequency selective voltmeter

I used a Sierra 303B for years. Sold it for $40.00.

jim vm

 

[spongella]

Thanks for the comments, much appreciated.

I found a Sierra 303B and am awaiting it's arrival.