The AM Forum

I use the ESP product detector and the am sync detector here in the shack. I guess he got alot of requests for an an in one unit and now we have it. THe PD3S.


The unit needs 455kc IF.  If you have an SP600 or R390 or 390A. This plugs in with the supplied BNC cable.  It will work with any 455KC receiver. I am using it with a National HRO60 through the Narrow FM Socket.  Three wires and your up and running.

THe video has crappy audio and I dont have a tripod so the entire video is pretty much crap. However, you can see what it looks like and get an idea of how it works. After setting the internal IF levels and tuning it better after the video, I got the SSB very smooth and clear.  I also spent some time listening to the chinese BC station (in english now) and the AM sync is really nice. The voices jump out of the muck.

I really like the PD3S.  Its also cheap at $140 for everything.  I dont know the guy and I paid full retail. So this guys opinion is not "biased".

http://youtu.be/veocXG45PVY

Putting those two in the same box is great idea.  I may have to splurge.

What do you think of the AGC performance? I noticed one of the product detector mods published in ER  engages a .33 uF cap to increase the hang time of the AGC when the radio is switched to CW. This is the one with the board mounted under the chassis with a relay that switches to the product detector in CW, not one of the ones that plugs into the NBFM socket -- May 2008, Decesari.

I imagine he did that for a reason. Is it a good enough reason?

Thanks for the video

The instructions suggested a delay cap on the AGC line.  However, I dont find it a problem. The AGC seems smooth to me on SSB.  This thing is really neat.

C

Clark, is that thing easy to disassemble?  I'd love to see a pic of the inside to see how he's doing the sync.  Perhaps the MC14122 chip?

They have a picture of the board on the website.

http://www.electronicspecialtyproducts.com/SyncPhoto500.jpg


I think it uses the chip you mention. I cant read the chip number. The guy was helpfull to me when I had questions so I am sure he will answer any questions.

What I like about the little unit is that it really clears up the sound and levels it out fades. You DO loose some LOW end response. Only very low end though.  I asked if the board did any filtering and was told no.  I then tested a low to high impedance transformer from the audio side of the unit to the HRO60. This has NO effect on sound.   

The SSB side is just fantastic.  I am serious when I say its as pleasant as my Icom 756pro on SSB.  The only issue is that most of these old rigs do not have enough ratio for SSB fine tuning so some of them are very touchy.

Also.  If I was serious about SSB use with this, I would probably change the AGC timing.  Right now it does not bother me and it works very very well.  But if you do find a weak station and a very strong station, You can tell that you wish the AGC was slower.

C

Thanks, Clark.  Unless there are more components on the other side of the board, it looks like it's actually a quasi-sync detector.  It has a couple of opamps and a MC1496 product detector chip.  What it's doing is taking the incoming carrier and running it thru a comparator which chops off the modulation.  That signal (which is just the carrier component of the signal) is then fed into the LO input of the MC1496.

The only disadvantage of the quasi-sync detector is that it won't ride thru deep carrier fades, but it's an extremely low-distortion AM detector otherwise.

Thats interesting.  It seems to work great.  Thanks for the info

It wants the IF right at 455, doesn't it? My selectivity crystal is almost a kHz (I mean kilocycle)  low, 800 Hz actually, so my IF is aligned at 454.2.

I did not find that this is a problem.  I did do a very careful IF alignment though.  It sure works great on SSB and AM.  The AM really clears up and makes the signal jump out of the speaker. 

C

Clark thanks for the review.  Have you found any problem listening to an AM QSO where stations are on slightly different frequencies?  The Sherwood upgrade included a seek-and-lock function to address that.

I would be keen to hear a recording, off a hard connection (not mic to speaker), to compare with and without.

As time permits.

No. I have not.  I have had this issue with SDR rigs with AM sync.  They try to lock on and skip. This one does not do that.

I am not sure how I would get an audio output from the HRO60.  I guess I would need a line to phono jack converter.  I might have to look into that.

The PD3 has an audio out.  But then you could not compare signals to the HRO with out. 

The main advantage is the clear audio and lack of noise in the Am sync mode.  The SSB is Driftless so it makes SSB very usefull on the HRO60.  My other SSB adapters Drift, The CE, the BW and even the TMC.  So now you have a drifting receiver and a Drifting SSB adapter. 

I have another AM sync unit and another SSB unit here.  I replaced the dual units with the one single PD3.  Is there someone that would like to run some lab tests?  I can send them out.
C

As JN noted a few post back, this is a quasi-sync detector. There should be no lock-up time and no associated heterodyne heard as the carrier frequency shifts from one station to the next.

I have been in communication with Ron at Electronic Specialty Products concerning a PD3S for my Gonset G-76 Transceiver. The Gonset detector/audio have issues, and on SSB reception it is very poor. The PD3S might be a big asset to this rig, but the 262 Khz IF adds a problem. For the SSB portion of the PD3S, this IF frequency adds $50 to the cost.

So I am weighing the SynC detector only and the heck with SSB.

Jim
WD5JKO