[MRCA] RF Generator wanted

Al Klase ark at ar88.net
Thu Mar 19 14:59:52 EDT 2020 

Ray and the group,

What you're talking about is a laboratory-grade signal generator. Here's 
a couple I know of first hand:

HP-606:  Tube based, Bigger than a braedbox, LF thru HF, calibrated 
attenuator, repairable, Most seem to work without a fuss.

URM-25:  Essentially a reduced-size military version of the HP-606.  
Many need to be recapped - that's a PITA but doable, Small size of the 
freq. dial is NFG for old eyes.

HP-6840:  400 KHz - through UHF,  Digital readout,  AM and FM 
modulation.  Someone mentioned the gear problem with the band switch.  I 
handle mine gingerly.  When one of these stops working it makes a nice 
wheel chock unless you're a talented technician with a lot of time on 
your hands.

Don't discount the old-buzzard General Radio stuff.  The 1001-A and the 
rally old 405 come to mind.

The Eico/HeathKit/RadioShack things are all toys.

Al




On 3/19/2020 2:29 PM, Ray Fantini wrote:
>
> Signal generation is easy, the problem now days is that I have reached 
> the point where I want to confirm receiver sensitivity at different 
> frequencies so you have to have the ability to calibrate the output of 
> the generator and a calibrated attenuator to be 100% that the radio is 
> working correctly. These early synthesized radios suffer from 
> insensitivity and in the case of USB only radios when trying to copy 
> AM if the time base in the radio is not dead on it can be an issue. 
> The GRC-106 receivers exciters RT-662/834 produce an annoying 
> heterodyne if not dead on carrier when used in AM mode. They use the 
> same product detector in USB or AM with only inserting a carrier in 
> the AM transmit mode to produce a quasi AM signal.
>
> The big Motorola 2000 series monitor produces signals at calibrated 
> levels but get the idea that the AM on it was only an afterthought, 
> when doing VHF or UHF FM its great but working on this old HF/SSB 
> stuff is requiring a different tool set. Had to come up with a power 
> meter that works down in the 2 to 30 MHz range along with things like 
> the two tone generator for testing the transmitters and amplifiers, 
> now I want to be able to provide a clean low distortion AM signal for 
> checking distortion on the receive side.
>
> Something like the things years ago when working with VHF FM stuff and 
> using the SINAD meter to tune for best audio.
>
> Have not pulled out one of the older Motorola Service monitors or a 
> Cushman  to see if it has better AM, have been saving them for you to 
> get you working with one.
>
> Ray F/KA3EKH
>
> *From:* comcast <kg2bz at comcast.net>
> *Sent:* Thursday, March 19, 2020 2:08 PM
> *To:* Scott Johnson <scottjohnson1 at cox.net>
> *Cc:* Ray Fantini <RAFANTINI at salisbury.edu>; 
> milsurplus at mailman.qth.net; MMRCG at groups.io; Mrca Mailing List 
> <MRCA at mailman.qth.net>
> *Subject:* Re: [MRCA] RF Generator wanted
>
> what about using an lm or bc221?
>
> Sent from my iPhone
>
>
> On Mar 19, 2020, at 12:09 PM, Scott Johnson <scottjohnson1 at cox.net 
> <mailto:scottjohnson1 at cox.net>> wrote:
>
>     My choice, for the last thirty years, is the HP 8640B.  I believe
>     it to be among the best generators for receiver measurement and
>     alignment.  The only problem is the nylon gears, which tend to
>     shrink and crack from the brass hubs.  There are people making and
>     selling gears, and even at $300 for a set that, it is still worth
>     owning one.
>
>     Options include a doubler to 1024 MHz, reverse power protection
>     (recommended),and variable frequency modulation.  The Military
>     version in the yellow case is to be avoided in my opinion, as it
>     lacks phase locking and is generally a pain in the keister, unless
>     you (like me) collect such things.
>
>     Scott V. Johnson W7SVJ
>
>     5111 E. Sharon Dr.
>
>     Scottsdale, AZ 85254-3636
>
>     H (602) 953-5779
>
>     C (480) 550-2358
>
>     scottjohnson1 at cox.net <mailto:scottjohnson1 at cox.net>
>
>     scott.johnson at ieee.org <mailto:scott.johnson at ieee.org>
>
>     *From:* mrca-bounces at mailman.qth.net
>     <mailto:mrca-bounces at mailman.qth.net>
>     <mrca-bounces at mailman.qth.net
>     <mailto:mrca-bounces at mailman.qth.net>> *On Behalf Of *Ray Fantini
>     *Sent:* Thursday, March 19, 2020 8:04 AM
>     *To:* milsurplus at mailman.qth.net
>     <mailto:milsurplus at mailman.qth.net>; MMRCG at groups.io
>     <mailto:MMRCG at groups.io>; Mrca Mailing List <MRCA at mailman.qth.net
>     <mailto:MRCA at mailman.qth.net>>
>     *Subject:* [MRCA] RF Generator wanted
>
>     Everything old is new again! Been working a lot with repairing a
>     lot of GRC-106 receiver exciters and noticed that my Motorola
>     Communications Service Monitor produces a lot of phase noise and
>     poor-quality AM on the HF bands. Decided that what I need is
>     something like an old school URM-25 or maybe if I can find one a
>     URM-144/SG-823 being I already have a SG-376 that I got last year
>     that I have been using a lot for SSB work.
>
>     As always not looking to spend a bunch of money on this but can
>     always do a trade. Lot of crazy prices for URM-25 generators on
>     eBay but use to seeing them at Hamfest for $20 to $50 price range.
>     Did not realize until recently that you more often than not need
>     vintage test equipment for working on vintage radios.
>
>     It’s amazing what happens when you take modern items like the new
>     generation of digital scopes today and look at things like
>     modulation levels for AM carriers! Or operate DVM in high RF
>     environments.
>
>     Ray F/KA3EKH
>
>     ______________________________________________________________
>     MRCA mailing list
>     Home: http://mailman.qth.net/mailman/listinfo/mrca
>     Help: http://mailman.qth.net/mmfaq.htm
>     Post: mailto:MRCA at mailman.qth.net
>
>     This list hosted by: http://www.qsl.net
>     Please help support this email list: http://www.qsl.net/donate.html
>
>
> ______________________________________________________________
> MRCA mailing list
> Home: http://mailman.qth.net/mailman/listinfo/mrca
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:MRCA at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

-- 
Al Klase – N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/mrca/attachments/20200319/588018d5/attachment.html>

More information about the MRCA mailing list