The AM Forum

Low balled an offer on a nice HP3325A on the 'bay which was accepted. I've needed a good signal source to align all this tube gear that's mysteriously appeared in my shack over the past few months. Would I need to do anything special to use the HP as a signal source for the Valiant in lieu of its "ROCK SOLID" VFO?

You going to be operating digital modes with the Valiant? That's a very big overdone oscillator to just hang on a Valiant. And do you really want to screw with the Valiant to interface these two things together? The existing VFO in the Valiant has served its purpose well for over 50 years.

I own an HP3325B and HP3324A for my lab. Feel free to ask if you run into operational difficulties. You can always externally AM modulate the generator and run QRP. No guarantees you'd do well on the 20-meter net!  :)

It's a very nice function and sweep generator. Very clean output. I know you'll enjoy it.

dan W7NGA
San Juan Island, Wa.

Thanks. I'm always trying something different, but I really need a FG as I have 3 receivers that require alignment. At some point I would like to at least try to drive the Valiant with the FG, but this would not be a permanent thing. I believe the specs list an outpoot range of 1 mV to 10 V on the HP. Do you think I will need to attenuate the outpoot to lower than 1 mV to align an IF chain in a receiver (eg. HQ180)??

I looked at the DDS synthesized units on the 'bay, and their low price was attractive while their bare circuit boards were not. I've been wanting to get a FG for some time. I've used Tek FG50* series way back in the days of college but they needed a mainframe apparently in which to plug into.

Low power AM qrp....that's one I had not thought of.

I think the 6CL6 is biased to -3V on the 1st grid. So my guess is it would not take a lot of drive; maybe 1.5V PP maximum as we don't want to drive the grid positive into conduction and pull current off the cathode. The inpoot Z on the 1st grid is around 500K???

No.

I use a 3325A to sweep align receiver IFs (with a log detector and scope).  It's a very useful piece of test gear.

Grant

I used a 3325A as the VFO for my GPT-750.  It has a higher output than most sig gens and it has a sweep mode that can be a pretty effective sideband eliminator  ;)

Its phase noise is pretty pisspoor though, so I use a HP8640B as a VFO instead.

Snot mine, but you could buy one of these (http://www.ebay.com/itm/HP-355B-VHF-ATTENUATOR-0-5W-50-OHM-DC-500-MC-/161420869579?pt=LH_DefaultDomain_0&hash=item25956effcb), or buy a couple cheep 30db attenuators to put in line.  That would get you down to a Micro-Volt or so.

How do you hamboners key those generators? Is there a jack on the back?

The sig gen would work using the ssb input getup. Just swap it over for use on AM. Hafta to key the generator to avoid backwave as Terry says. 

not sure if this discussion is still steeped in reality .. you can key the HP3325B via gated AM modulation by keying a +5v DC bias at the AM Mod input port. I am assuming the HP3325A is similar.

I have actually heard someone on 15-meters using a sweep generator. Wasn't me ;D

I didn't key mine, although the bias on the AM input is an outstanding idea that I never thought of!  I just used double shielded coass to the xmitter and the backwave was weak enough it was never really an issue.

Unit came in today. It appears to be the version that works up to 60 MHz (out the back). Its working fine. Not bad at all for what I paid for it.

 


   Congrats,


         Harmonics R Us...  Prolly gud to two metros....

/Dan