[BULK] - [Amps] 2m Linear Amp Enquiry

[R.Measures]

On Sep 10, 2004, at 2:25 AM, Ian White, G3SEK wrote:

> Steve Thompson wrote:
>>> Search around for the W2GN design using a pair in parallel, it works 
>>> a
>>> treat. I modified the grid circuit to have separate bias control, so 
>>> it
>>> will work with unmatched tubes. Personally, I don't like link 
>>> coupling -
>>> it's possible to get false indications of optimum loading.
>> Ooops - what I meant was - tuned link coupling. A variable untuned 
>> link should give you monotonic loading adjustment, the same as a 
>> variable series capacitor.
>>
>
> Should, but probably won't. Most link-coupled VHF/UHF amps suffer from 
> chronic under-loading, because it's very difficult to make the link 
> coupling tight enough to load the tube(s) correctly.
>
Good point, Ian.  In the 2, 4cx250R 144MHz amplifier I built, I finally 
resorted to making the link out #12 TFE-insulated wire and laying it 
against the gnd-end of the tank-L.  Since the resulting screen-I was c. 
1mA, I knew the loading was  adequate.
cheers

> In contrast, capacitively-coupled VHF/UHF amps tune and load as easily 
> as a pi-network.
>
> The W2GN articles appear to be downloadable from:
> http://www.newsvhf.com/w2gn.html
> (I wasn't able to verify that - please can someone confirm?)
>
>
> -- 
> 73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
> http://www.ifwtech.co.uk/g3sek
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>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org