Adding a VFO to a Pace Sidetalk 1000B

[Justin B.]

After my successes with adding a VFO to my pair of Midland 13-898Bs I pulled my old Pace Sidetalk off the shelf and started messing with it. Here are some observations:

1. The VFO can be added using the same method as for the Midland.
2. The "standard" sine wave output (1V PP)from the DDS module is insufficient for the Pace.
3. Using the nasty looking 5V square wave appears to provide enough drive but I am going to build a little buffer amp so I can use a sine wave.
4. Sensitivity and power out drop like a stone above around channel 28. I will have to re-align the radio centered on a higher frequency. The Midland seemed to be more tolerant of the increased range.

That's all for now and will update when/if I decide to tinker further with increasing the freq range.

73,

 

[nomadradio]

If it just needs an amplitude boost, I sell a board on fleabay that does this.

https://www.ebay.com/itm/1172621335...pid=5336136228&customid=&toolid=10001&mkevt=1

Has a trimpot to set the desired drive level.

It ain't cheap, but the schemo is posted in the sale listing. Nothing exotic in it.

It's biased to run from unregulated 18 Volts DC the Siltronix 90's rectifier bridge. Might need to change one resistor feeding the transistor's base for a 14-Volt supply. Haven't tried that.

Second thought: Could the input impedance to the radio's two mixers be low enough to be loading down the 9850's output? Don't know what impedance it's meant to match. If so, a simple RF JFET source follower might fix that problem. It's dirt simple, three disc caps a N-channel JFET and one resistor. Used that trick to drive a counter input a few years back and wrote it up here. Not sure what search term I'd have to use to find it.

73