Batboard

Does anyone have some quick and dirty info on the Range 2, UHF Syntor VCO.

I'm using a PIEXX module, was working great and now VCO won't lock up.

Thanks in advance.

Chuck,

WB6YOK

Difference in temperature perhaps? I don't know how picky the original Syntor is, but i have had Syntor X's that would lock fine in fair weather and be picky when cold.

Weird that it worked then suddenly quit.

You said it is a Syntor, so I assume you mean the original Syntor with the Piexx Syntor Revival product installed.

It would be nice to know how long it has been running for total (how long you have used it). More than an hour... and where. In a mobile installation or at home. How many different frequencies will not lock? Is it just frequencies near the band edge that do not lock?

Did you do any major reprogramming just before it died? Did you do anything at all to it just before it died? If you are using a computer to run it, is the computer and all of its cabling OK? Again, if you are using a computer, did you install any software on your computer just before the VCO problem occurred?

You have to consider component aging in the VCO might have changed its frequency operation range (this is more of a slow onset problem). If you modified the VCO tuning strip, does it it still appear to be in good shape? However, something like a cold solder joint is more likely. These can be the problem behind the “it WAS working just fine until...” complaint.

Have you looked for any loose connectors? Have you unplugged, examined, cleaned and/or reseated any connectors? Have you looked at the VCO steering voltage with a meter (it would be telling if the steering voltage was always stuck at one end or the other, no matter what frequency was entered)?

Actually, to be precise, the setup is not Syntor revival. I'm using PIEXX's code plug replacement in a UHF Syntor X.

The radio is completely stock. When I first fired it up it locked right up and talked great!

The area where it is located is awfully cool though. The only issue I have is that you would think a Motorola radio would work in a broad variety of environments.

Still, I am pushing it a bit in ham service, it might be flakier environment wise than I might otherwise suppose.

We'll see. That's the joy of ham radio, right?

Motorola Syntor X radios are able to function in a broad variety of environments. A range 2 UHF Syntor X is for 450-470 MHz.

You might need to change the tuning on the VCO for HAM use:
http://www.open.org/~blenderm/syntorx/efreqx.html

Which I am perfectly willing to do. Trouble is I can find almost no info on a UHF VCO. Everything I can find seems to be about the VHF radios. Which was the point of the original post in the first place.

The UHF has a similar tuning strip, however it is a T shape with 13 pads total. 7 pads on one side and 5 pads on the other side of the main feed point pad. You have to experiment with these to get them right. These may be more sensitive to being off its frequency/range than the VHF one when its cover is removed, so testing should be done with the cover back in place. The basic theory is exactly the same for the VHF and UHF.

I think your PIEXX module also has settable VCO tuning points you can change to match the retuned VCO. The tuning points are the frequencies where one of the 4 VCO sub-tuning ranges are selected.

The frequency you program into the VCO can only try and steer the VCO frequency to match, but if the VCO frequency range is wrong it will never be able to reach the programmed frequency (the steering voltage will be stuck at a minimum or maximum value). The VCO frequency programming includes which VCO frequency range is used. So, the programming has to synchronize with the frequencies the VCO can reach for its programmed range. The Syntor X microprocessor can not see the VCO lock state, so it has no idea what is going on. However, the VCO unlock state does block any Tx activity. Newer radios like the Spectra microprocessor can see the VCO lock state. With the Syntor X all you have is the LED that pokes through the RF board so you can see it with the radio drawer top cover off.

I was going to ask what the status of the VCO lock/unlock LED was.

It would be easy enough to see if it's temperature related by using a hairdryer to warm up the VCO and then see if it locks again.