[MRCA] RF Generator wanted

Fri Mar 20 23:05:36 EDT 2020

HP8656B - programmable stops no cranking, just a thought.

On 3/19/2020 4:09 PM, Scott Johnson wrote:
>
> As far as I know, with the exception of some other more exotic HP 
> synthesized generators, the 8640B has the widest output amplitude 
> range out there. (-140dBm to +20dBm)  It has a very well shielded 
> attenuator that is supremely accurate, and is free from spurs and 
> intermod products, because it is a cavity oscillator that is divided 
> down to the operating frequency.  It can then be phase locked for 
> stability.  Nothing comes close for receiver measurements.  It does 
> require TLC now that it is at least middle aged, but it is modular, 
> and comes apart like a set of Legos.  Parts are available, as there 
> are many donor unit out there.  Don’t discount it.  The HP 606B with 
> the 8708A PLL unit is a nice second place, although even older and 
> bigger. (I have a late model beige cabinet one, built in the early 
> seventies!, as are the older fluke synthesizers such as the 
> 6060,6080,8080, etc.  The URM-25 attenuator is not particularly 
> accurate, and will not stay accurate even if calibrated (I have had a 
> half dozen, the URM-25F is somewhat better in this respect).   
> Presently , my general use Signal Generator is an HP/Agilent/Keysite 
> (made through all three eras) 8648B, which fulfills 90% of my testing 
> needs.  It is available used for around $400. And it is nice, compact, 
> and lightweight.  Covers 9 kHz-2000MHz, and has -136 dBm to +13 dBm 
> attenuator range.  Models A-D are frequency ranges ( A is 1000MHz, B 
> is 2000, C is 3200, D is 4000).
>
> 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 <mrca-bounces at mailman.qth.net> 
> *On Behalf Of *Ray Fantini
> *Sent:* Thursday, March 19, 2020 11:29 AM
> *To:* comcast <kg2bz at comcast.net>
> *Cc:* Mrca Mailing List <MRCA at mailman.qth.net>; 
> milsurplus at mailman.qth.net; MMRCG at groups.io
> *Subject:* Re: [MRCA] RF Generator wanted
>
> 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 <mailto:kg2bz at comcast.net>>
> *Sent:* Thursday, March 19, 2020 2:08 PM
> *To:* Scott Johnson <scottjohnson1 at cox.net <mailto:scottjohnson1 at cox.net>>
> *Cc:* Ray Fantini <RAFANTINI at salisbury.edu 
> <mailto:RAFANTINI at salisbury.edu>>; 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:* 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
>
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