RF Frequency Synthesizer Recommendations

[W2XR]

I am looking for an RF frequency synthesizer that meets the following basic requirements. Does anyone have any supplier/model number recommendations, or perhaps a unit that meets these requirements?

Frequency Range: 2 to 5 Mhz., min.
Resolution: 10 hz min., 1 hz. desirable
Frequency Control: Continuous rotary knob. Keyboard entry of desired frequency is not acceptable
Frequency Display: Digital display of output frequency.
Output Voltage: 1 Volt RMS min., across 50 ohms
Spectral Purity: All spurs better than -60 dBc
Packaging: Ideally Rack-mountable to mount within a standard 19-inch equipment rack. Stand-alone package acceptable. Max. height: 7.0-inches
Ambient Operating Temp.: Room temp., benign-conditioned, ground-fixed environment
Operating Power: Nominal 120 VAC @ 60 Hz.

I am not too concerned about phase noise, jitter, or absolute frequency stability vs. ambient operating temp.

The application for this device will be as the VMO/VFO for a TMC 2KW PEP SSB rig I am integrating from the major assemblies I pulled from a TMC GPT-40K SSB xmtr a number of years ago.

And of course, cost: <$300.00 if possible. Used equipment is expected at this cost point.

Thanks for any possible recommendations, based upon my application and specs.

73,

Bruce

[k4kyv]

I think this may be just what you are looking for, if the company is still in business.  I picked up their earlier model, brand new at Dayton about 10 years ago for < $100.  The only thing I have used mine for was as a rock-stable VFO for my 10m rig back before the band fizzled, and as a test signal source with 1 Hz steps. 

I can turn the unit on, set the frequency to 10 or 15 mHz, then turn on the receiver, and it is always within a few Hz of WWV.

For my regular VFO, I still use my modified T-368 M.O. unit with regulated plate and filament voltage, which is almost as stable, and a little less hassle to use.  My older version DDS VFO is somewhat a PITA because it drops back to a default frequency every time you turn it off, but I believe the later version remembers the last frequency it was set for, when it is powered back up.

[WB2YGF]

I had not seen that one

I was looking into this one.  $59 for the complete kit.

http://www.pongrance.com/

[Mike/W8BAC]

Don,
Did you happen to take notes or draw up a schematic for the power supply used on the T-368 MO? I'll have one soon and need to build a supply.

Bruce,
I use an HP 3320B frequency synthesizer here from time to time. Output is zero -70 Db (edit; that should read zero - 20 Db output, thanks JN) and works fine as a crystal replacement. Very clean and stable. No counter, just thumb wheels. Other later versions might get you closer to what your looking for. This one was $50.

Mike

[w3jn]

The HP 3320 is very cheap and is 0-13 MHz and up to about 20 dBm output IIRC.
I use a HP3325A (keyboard input) on my GPT-750.  Has up and down arrows to VFO the frequency in any selectable step though.

[W2XR]

Mike and John,

The HP 3320 looks interesting and may suffice for my purposes.

But, what is the minimum resolution of this unit? If I'm not mistaken, I think it is only 1 Khz. I'm looking for 10 Hz resolution, minimum.

Can you verify this for me?

John: BTW, this is to replace the enormous & heavy TMC VOX-5 in my rig. The VOX-5 works great, but it is very large, heavy, difficult to maintain, and extremely inefficient relative to what is available nowadays with respect to frequency generation. It also takes forever to QSY; it' s not very frequency agile. As you know, I'm a tube guy, and I'm still saying this!

I appreciate the guidance here from everyone!

73,

Bruce

[Mike/W8BAC]

Bruce,

In the MHz adjustment position you can fine tune four places to the right of the decimal with a vernier on the last digit.

Mike

[k4kyv]

Don,
Did you happen to take notes or draw up a schematic for the power supply used on the T-368 MO? I'll have one soon and need to build a supply.

I could get out my documentation and scan it for you.  I did a tremendous amount of modification on the unit before putting it online.  It would be extremely difficult to ever get it to work in a T-368 again.

I use an external power supply with two filament supplies.  When everything else is turned off, the oscillator tube still is in the circuit, running off a 6.3 vac power supply.  When I turn on the rest, it transfers over to a regulated DC supply.

[w3jn]

There's a 3320B up on eBay right now, $25 no bids with 18 hours to go.

http://cgi.ebay.com/HP-3320B-Frequency-Synthesizer-26-99-dBm-Max-Output_W0QQitemZ310121032434QQihZ021QQcategoryZ1504QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

The most irritating thing about the VOX VMO is it takes a million cranks of the knob to go from one end of the band to the other.

[WA1GFZ]

HP3325 has a nice sweep mode that would make a great SBE function.

[Fred k2dx]

Is there an easy way to 'key' the HP3325?

[w3jn]

Indeed it does, Frank 

Fred, no it doesn't.  Runs continuously.

[Mike/W8BAC]

JN is right Fred. I use a BNC 50 ohm relay to switch the synthesizer into a small 50 ohm load (hardly bigger than a BNC connector) on receive than to the transmitter just before the finals need the drive.

Mike

[W3NP]

I use a Fluke 6011A signal generator as the VFO for my Gates BC-1G, my HB 812H pushpull rig, and my Meissner 150B using a switch box to route the output to the proper rig. I poked around inside the 6011 and found that if I removed a 24 v line to the output board, the unit was inaudible in my station rx, even with a quiet band. I just installed a small relay in the sig gen and the main station keying line keys it up when going into tx.

[WA1GFZ]

You could key any oscillator running around 0 dBM using a double balanced mixer input is RF in output is LO. Load the IF port with 50 ohms to ground. You key the DBM by sourcing around 10 ma of current into the IF port with a resistor to a 5 or 12 volt source. You can slope control it with an RC to eliminate clicks for running CW.

[KB3DKS]

I use a Fluke 6011A signal generator as the VFO for my Gates BC-1G, my HB 812H pushpull rig, and my Meissner 150B using a switch box to route the output to the proper rig. I poked around inside the 6011 and found that if I removed a 24 v line to the output board, the unit was inaudible in my station rx, even with a quiet band. I just installed a small relay in the sig gen and the main station keying line keys it up when going into tx.

 I use a PTS 040 synth here and BNC relays for routing and muting. Nice thing about the PTS is that the output level control is via dc voltage so an additional relay can also set the level to match what the transmitter wants to see or checking zero beat.

Bill, KB3DKS in 1 Land
 

[KB2WIG]

FWIW,

LM-21  aka, BC-221

these babies can be found cheep, and are very boat anchorish..

 out of the shockmounts , and side by side with the power supply, the equipmnets will fit in a 7" X 19" space


klc

[KF1Z]

I had not seen that one

I was looking into this one.  $59 for the complete kit.

http://www.pongrance.com/

Seems a bit expensive. ($170 as a kit) That's the one Don pointed to....

For half that price new, you could build the NORCAL  QRP club  FCC1/FCC2.  ($85 as a kit)
Doubles as a Counter and DDS.

If you're looking at a DDS , I'd recommend that one....
Hard to beat the price....more bells and whistles than the $59 unit.

Uses a better clock and generator too.


Of course, you may not want to build a kit and mount it in an enclosure and all that...

Plus, I think they just BARELY put out 1 volt pk-pk across 50 ohms

I could measure mine to see.......

[WB2YGF]

For half that price new, you could build the NORCAL  QRP club  FCC1/FCC2.  ($85 as a kit)
Doubles as a Counter and DDS.

Looks like a nice unit.  Unfortunately, the FCC2 is not currently available.

[k4kyv]

For half that price new, you could build the NORCAL  QRP club  FCC1/FCC2.  ($85 as a kit)
Doubles as a Counter and DDS.

Looks like a nice unit.  Unfortunately, the FCC2 is not currently available.

Out of stock
Look for the revised FCC-2 Mk2
To be released soon

The $59 N3ZI kit has cleaner output than the present S&S Engineering unit.  Mine is the older version, which is comparable to the N3ZI unit it spectral purity, but it  doesn't have enough memory to hold the last setting , so you cannot turn it off during standby periods without it defaulting back to a predetermined frequency.

Unfortunately, all these kits use SMT technology, which is not designed for manual soldering but for robotic assembly, although all the kit producers claim it is not difficult to do by hand with the proper tools.

Here are a couple of issues I have with the information given on the NorCal site:

(1) Looks like they plan to put it back into production, but does anyone know what the price was before it went out of stock?  The FCC-1 is only $35, but I found no clue what to expect for the FCC-2 if/when they start producing it again.

(2) The N3ZI unit has resolution down to 10Hz per click.  I like the 1 Hz resolution on my S&S Eng unit; I think 10 Hz per step would be the minimum (or should I say maximum?) acceptable capability.  But NorCal doesn't say what the FCC-1/2 combo's finest click resolution is/was.

[w3jn]

I bought one of N3ZI's cheapo counters, to replace a smashed LCD in a pro marine receiver.  The PC board is absolutely top-notch quality, as are the parts he supplies.  I had a few issues with RF cornfusing the prescaler flippity-flop, added a few bypass caps and all was well.

That little DDS VFO of N3ZI's looks Fine Business indeed.  Just one little 16 pin SMD bug to slobber in.  BTW the phase noise in these DDS units is highly dependent upon the ref oscillator.  A better ref osc might offer even better phase noise.

Still, I don't like a standalone DDS for the spurs.  If you look at the data sheet for the DDS chip N3ZI uses, certain divide ratios provide fairly horrible spurs.  Better would be to use it to drive a bank of lo-noise PLLs so the spurs are stripped off.

[Steve - WB3HUZ]

If it's for VFO use, wouldn't any spurs be stripped off by the tuned circuits that follow it? Or are the spurs very close in?

[KF1Z]

Unfortunately, all these kits use SMT technology, which is not designed for manual soldering but for robotic assembly, although all the kit producers claim it is not difficult to do by hand with the proper tools.

Here are a couple of issues I have with the information given on the NorCal site:

(1) Looks like they plan to put it back into production, but does anyone know what the price was before it went out of stock?  The FCC-1 is only $35, but I found no clue what to expect for the FCC-2 if/when they start producing it again.

(2) The N3ZI unit has resolution down to 10Hz per click.  I like the 1 Hz resolution on my S&S Eng unit; I think 10 Hz per step would be the minimum (or should I say maximum?) acceptable capability.  But NorCal doesn't say what the FCC-1/2 combo's finest click resolution is/was.

The FFC-2 MKII has already been in production, and they ran out.
The price is $50 with the DDS IC. (Plust the $35 for the FCC-1)

The smallest step size is  1hz.
(I believe all that info is in the .PDF manual at the bottom of the info page)

By the way... this makes a decent audio test generator as well....


The FCC-1 is ALL regular through-hole components.

The FCC-2  is all SMDs  it was my very FIRST attempt at surface mount soldering...
Took all of an hour to finish.


The hardest part was the 20 pin AD9834... errrr solder bridges....
But a couple minutes with some wick cleaned it up quick.

And NO, I'm not 'old and shaky'... but I do solder every day..
And need plenty magnification even with through-hole components....

Now I almost prefer SMD...  get sick of cleaning up piles and piles of lead clippings!
(man it hurts to get those in the bottom of your bare feet too !!)

[w3jn]

If it's for VFO use, wouldn't any spurs be stripped off by the tuned circuits that follow it? Or are the spurs very close in?

Some are fairly close in, from the AD data sheet.  ANd if you're gonna use it in a receiver there generally aren't any tooned circuits between the osc and the mixer.

[KA8WTK]

Don,
  I bought my FCC1 and FCC2 at Dayton. I seem to remember that the FCC2 was about $30 without the synth chip and $45 with the chip. The FCC2 kit comes with a new EEPROM to plug into the FCC1 when they are mated-up.
 I'll see if I can get more "resolution" around that price.

Bill KA8WTK