[Central-Electronics] 10B Mod

[George Maier]

Wow - it's absolutely super to see so much activity on the CE reflector.

Power output from a 10B (or 10A) at around 5W or is pretty normal in my
experience.  I find it difficult to drive a 600L to full output with either
transmitter.  The 20A is a whole other story; no problems with drive. 

As Jim C noted earlier, there a lot of options for a VFO, but none are very
common.  The Lakeshore is the easiest by far.  Second in line would be a 458
VFO, but they can really drift.  I wound up replacing every resistor and
capacitor in mine before it settled down. I did one more thing that added
the frosting to the cake, however; replaced the old selenium rectifier used
for the 1626 oscillator filament with a modern silicon bridge and a 12V
Zener regulator.  Now I run both the 1626 oscillator and 1625 buffer
filaments on DC, and it's very stable indeed. 

Colin, you mentioned the HT-32, and you're on the right track. If you can
find an HA-5 VFO, it's the same oscillator, and could be used for a CE
exciter just by converting the 6M or 2M position to a straight through
buffer in the 5.0 MHz range. 

Keep it up people; this is great!

73, George - W1LSB


-----Original Message-----
From: central-electronics-bounces at mailman.qth.net
[mailto:central-electronics-bounces at mailman.qth.net] On Behalf Of k7fm
Sent: Tuesday, November 10, 2009 9:36 AM
To: Jim Candela; central-electronics at mailman.qth.net
Subject: Re: [Central-Electronics] 10B Mod

Hi Jim:

If you are looking for an even easier way to temperature compensate an 
oscillator, you could always use the method used by Hallicrafters in the 
HT-32.  In that circuit, a differential capacitor is used, with one side 
tied to a NP0 cap while the other side is tied to a N1500 cap (or something 
like that).  Then, you can change the compensation to anything between 
nothing and -1500 ppm.  Simply turn the screwdriver adjust capacitor until 
drift stops.

73,  Colin  K7FM 

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