I used to use a 50 Ohm Cantenna in parallel with the input, and never
bothered to remove the 350 Ohm assembly (why bother? leaving it there
results in 43.75 Ohms) and that worked fine.
The T-bolt could be tuned to produce about 1 kW PEP output with the grid
current just perceptably ticking the meter's needle, if it was loaded
properly (heavily). An advantage of the passive/swamped input and
roller-inductor output network is that it will cover any frequency between
3.5 and 30 MHz quite effectively, so EFJ accurately predicted the
availability of the WARC bands 20 years in advance. They also guessed about
the possible new 60m band.
In my exp, the T-bolt could not be tuned to >1kW PEP out and remain linear;
the HV is obviously too low for that. But it always sounded good at 1kW,
and a good sounding kW is far better than a crappy sounding 2kW any day of
the week.
WB2WIK/6
"Each success only buys an admission ticket to a more difficult problem." --
Henry Kissinger
> -----Original Message-----
> From: Bill Russell [SMTP:willy@global2000.net]
> Sent: Tuesday, November 06, 2001 5:39 PM
> To: amps@contesting.com
> Subject: [AMPS] More t'bolt questions
>
>
> Many thanks for the relays to my first post. A couple of points I left
> out.
> The t'bolt is tuned qrid input with one exception. It has a RES input
> position which is used for any exciter that will load into a 350 ohm load.
>
> RES means resistor. The is a 350 ohm resistor that terminates the exciter
> in this position. It is used in the am and ssb modes. Since modern
> equipment will not load into this I was hoping to change this resistor to
> 50 ohm. This RES position disconnects the tuned input and places this
> above
> mentioned swamping resistor across the grid ckt of the 4-400's. For some
> reason this position is NOT used for cw operation. The amp runs class C
> for
> cw and runs class AB2 for am and ssb.
> The HV power supply uses the following: 4800 VCT at 500 mills HV
> transformer. Choke input filter with a swinging choke. 25 hy at 80 mills
> to
> 5 hy at 500 mills. Filter cap is 8 MFD oil at 2000VDC although the hv is
> 2200 volts! It has a bunch of 0C3's in a separate screen supply for
> regulation (4). Ill give more info on the grid supply later (after I
> figure
> it out!)
> I would like to either improve the HV supply and increase the plate
> voltage
> if u folks think it would be a good idea or leave the HV as is and maybe
> increase or improve the HV filtering. I know if I increase the HV, ill
> have
> to change the screen and bias voltages to maintain the tubes at proper
> class of operation. A few months ago I emailed Mr. Measures about this amp
>
> and he said I should change the HV filter to a resonant choke filter for
> SSB
> operation. One more thing........the tubes are at grounded cathode but the
>
> rig does NOT use center tapped filament transformers. It uses 1
> transformer
> with 2 separate secondary windings, 1 for each tube. At the tube , one
> side
> of the filament is tied to ground and there are 2 .005 caps tied across
> the
> filament terminals of each tube. I always thought this was a bad idea
> because this only one side of the filament is at DC ground, not both sides
>
> as it would be with the center tap of the filament transformer tied to
> ground. I hope u all got that!!!!
> Again folks, thanks in advance...........more to come!!!
>
> One off topic question.................when ppl post anything to this
> group, I get the posts twice.......hmmmm.
>
> Bill Russell
> KC2IFR
>
>
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