Exciter identification

[intermod]

Hi, can anyone identify this exciter for me? I'm after the DIP switch settings

IMG_20200504_211418.jpg

[Bton-FM]

That is the Dawson exciter .The divider is 4049 N counter look up the datasheet and it will explain.

[RF-Head]

Correct it is a Dawson driverboard and it use a 74hc4059
There were many of them 10-20 years ago search the forum for more info
http://electronics-diy.com/1-watt-pll-f ... mitter.php

[teckniqs]

They can be a pain to tune, thankfully it's been many years since I used one of those.
Sometimes you have to change one of the capacitors to get it to lock depending on which part of the band you're using and what cap was already in there.

....And as far as I am aware no one has actually written down all the settings for each frequency and you have to work them all out.

p1.jpg

[teckniqs]

Page 2
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Page 6

[Albert H]

A slightly later version of the board had NPO capacitors in the oscillator, and came with two slugs for the VFO coil - a ferrite one for the lower part of the band, and an aluminium one for the upper part. A further refinement to the board gave a doubler driving a bandpass filter, so that none of the ½f got through at all. The final versions had an option for an MRF237 to give around 4 Watts.

[Bton-FM]

Hmmm Albert it’s a bit strange it uses BSX20s ......

[teckniqs]

Or 2n2369a

....Plus the final BSX20 stage can get quite hot and cause the power to drop, so I used to solder a little solder-tag onto the top of it to keep it cool or fit it with a little TO18 heatsink.

[Electronically]

Dawson driver

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[Electronically]

Dawson driver

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[Electronically]

Dawson driver

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I remember looking at this when jugglingpirate.net had this Dawson board was a good write up about it.

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[teckniqs]

Dawson driver

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That one looks like it's got a couple of ZTX313s instead of the BSX20's, makes a lot more sense.

[Electronically]

Dawson driver

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That one looks like it's got a couple of ZTX313s instead of the BSX20's, makes a lot more sense.

Yup teckniqs your spot on
Q1 – BSX20
Q2 – BSX20
Q3 – BSX20 (or ztx313 on older boards)
Q4 – BSX20 (or ztx313 on older boards)

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[teckniqs]

You could also use ZTX327 but they did a bit less power, which was ideal if you needed less than 1w and I used to usually get about 1.3w out of these which was a bit too much sometimes.

[Electronically]

You could also use ZTX327 but they did a bit less power, which was ideal if you needed less than 1w and I used to usually get about 1.3w out of these which was a bit too much sometimes.

Could do as it seems output works from 500mw to 1.2 Watts. But with your idea possibly 1.3 Watts.

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[teckniqs]

I put a Motorola 2n4427 in one of these once and got about 1.8w out of the thing.

[Electronically]

I put a Motorola 2n4427 in one of these once and got about 1.8w out of the thing.

Yea from the read up it mentioned it had 2n4427 Motorola which gives it more power. If you got 1.8 out of it then that's good.

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[teckniqs]

Best to use a better heatsink for them though, like the TO39 one that's twice as long.

[Electronically]

Best to use a better heatsink for them though, like the TO39 one that's twice as long.

Yea longer the heatsink is should keep it cooler. This driver was running a 150watt amp with 28volt 10 amp supply 300va toroidal was used to run it all in one box pretty tidy it was.

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[Albert H]

It's funny that these were called the "Dawson Driver" as it was actually "Kenny Myers" of RFL who designed them. I believe that the first PCBs for these were done by a guy who used to live down in Shirley (near Dawson's old place) and who ran "SLR".