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Transmitter Circuit



 
 
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  #11  
Old January 26th 11, 07:03 AM posted to rec.radio.amateur.boatanchors
coffelt2
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Posts: 70
Default Transmitter Circuit


"Nordic Breeds WA4VZQ" wrote in message
...
"Edmund H. Ramm" wrote in message
...
In "Nordic Breeds WA4VZQ"
writes:

[...]
Neutralization becomes more of an issue the higher you go in frequency.
Most simple entry level transmitters using a single 6146 in the 1950's
and 1960's were not neutralized as the 6146 was only used "straight
through" on 80 or 40 meters. On higher bands it was used as a frequency
multiplier/power stage. The Eico 730, the Elmac AF67, the Heath DX-20,
DX-35, and DX-40, and the Knight T60 used no neutralization.


Nor does the E.F. Johnson Viking Ranger. But it's CW-only variant,
named "Navigator" IIRC, does.

The Eico 723, the Heath DX-60 and the Drake 2NT. however, did.


The Drake 2-NT has a 6HF5 line output valve in the PA stage.


Several of the transmitters I named also used TV sweep tubes. In general,
all of the higher power TV sweep tubes have a higher perveance than does a
6146. In the case of the 6HF5, the transconductance (plate amps/grid
volts) is 1.6 times that of the 6146. My point was that with reasonable
layout, neutralization would not be required. All of these transmitters
multiplied in the final above 40 meters. If the plate is tuned to a
harmonic while the grid is tuned to the fundamental, there is far less
need to neutralize.

73, Barry WA4VZQ


You are surely correct there, Barry. I guess my homebuilt rigs never
multiplied in the final stage. I did try multiplying with a 211 (VT-4C)
triode in the final (read BC-375), but the power output instrument (75 watt
light bulb) was not impressed. (it did, of course have elegant Hammarland
neutralizing condensers in the plug-in tuning units)

Old Chief Lynn, W7LTQ

  #12  
Old January 28th 11, 12:35 AM posted to rec.radio.amateur.boatanchors
Nordic Breeds WA4VZQ[_2_]
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Posts: 12
Default Transmitter Circuit

"Edmund H. Ramm" wrote in message
...

Several of the transmitters I named also used TV sweep tubes.
[...]


Yes, all several two of them: Eico-723 and Heathkit DX-20, apart
from the Drake 2-NT already pointed out by me. Which means they don't
belong in a discussion about true transmitting valves (807 and 6146),
and their respective merits regarding neutralisation.

BTW, the above mentioned Eico-730 is a modulator.

73, Eddi ._._.



I think I am detecting a hint of sour grapes here, Eddi. My post was a
reply to Ken Scharf's post saying the 6146 would be more stable than the
807 because of its higher perveance and lower lead inductance. The TV
sweep tubes generally have considerably higher perveance than the 6146.
As for lead inductance, some TV sweep tubes had exceptionally long leads
to reduce "blivets" (a.k.a. snivets, VHF parasitics sometimes associated
with Barkhausen oscillation); these were unsuitable for use in
transmitters above 7 MHz or so. One lot of 6HF5's ran the cathode lead
from the top of the tube to the base; these barely worked on HF [Bill Orr
W6SAI, "Full Blast" Operation of TV Sweep Tubes, Ham Radio, April 1968].

Yes, the Eico 730 was a typographical error. It should have been Eico
720. The DX-20 used a 6DQ6A which has only slightly more
transconductance than the 6146. The Knight T-60 also used a 6DQ6. The
AF67 used a 6146 with no neutralization. (Another rig I did not mention
was the Eico 753 which used a pair of 6DQ6's _without_ neutralization but
in AB1 linear mode. Of course, in AB1 it could not frequency multiply in
the final.) The 6146 has only a slight increase in gain over the 807.

As to whether receiving and TV sweep tubes should be included in the
discussion, 6L6 tubes have been used by hams in transmitters since the
1930's. In fact, the 1614 was a 6L6 designed for RF service. RCA even
notes that curves for the 807 apply to the 1614 within its maximum
ratings.

The original poster, Radio Vintage, wanted a simple 2 or 3 tube 80/40
meter transmitter with VFO. For circuit ideas, I believe that the large
number of articles using TV sweep tubes should not be ignored. The
discussion was not specifically about neutralization. I suggested
doubling in the final as a means to simplify the design in that
neutralization would likely be unnecessary.

73, Barry WA4VZQ


  #13  
Old January 29th 11, 01:34 AM posted to rec.radio.amateur.boatanchors
Kenneth Scharf
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Posts: 136
Default Transmitter Circuit

On 01/27/2011 06:35 PM, Nordic Breeds WA4VZQ wrote:
"Edmund H. wrote in message
...

Several of the transmitters I named also used TV sweep tubes.
[...]


Yes, all several two of them: Eico-723 and Heathkit DX-20, apart
from the Drake 2-NT already pointed out by me. Which means they don't
belong in a discussion about true transmitting valves (807 and 6146),
and their respective merits regarding neutralisation.

BTW, the above mentioned Eico-730 is a modulator.

73, Eddi ._._.



I think I am detecting a hint of sour grapes here, Eddi. My post was a
reply to Ken Scharf's post saying the 6146 would be more stable than the
807 because of its higher perveance and lower lead inductance. The TV
sweep tubes generally have considerably higher perveance than the 6146.
As for lead inductance, some TV sweep tubes had exceptionally long leads
to reduce "blivets" (a.k.a. snivets, VHF parasitics sometimes associated
with Barkhausen oscillation); these were unsuitable for use in
transmitters above 7 MHz or so. One lot of 6HF5's ran the cathode lead
from the top of the tube to the base; these barely worked on HF [Bill Orr
W6SAI, "Full Blast" Operation of TV Sweep Tubes, Ham Radio, April 1968].

Yes, the Eico 730 was a typographical error. It should have been Eico
720. The DX-20 used a 6DQ6A which has only slightly more
transconductance than the 6146. The Knight T-60 also used a 6DQ6. The
AF67 used a 6146 with no neutralization. (Another rig I did not mention
was the Eico 753 which used a pair of 6DQ6's _without_ neutralization but
in AB1 linear mode. Of course, in AB1 it could not frequency multiply in
the final.) The 6146 has only a slight increase in gain over the 807.

As to whether receiving and TV sweep tubes should be included in the
discussion, 6L6 tubes have been used by hams in transmitters since the
1930's. In fact, the 1614 was a 6L6 designed for RF service. RCA even
notes that curves for the 807 apply to the 1614 within its maximum
ratings.

The original poster, Radio Vintage, wanted a simple 2 or 3 tube 80/40
meter transmitter with VFO. For circuit ideas, I believe that the large
number of articles using TV sweep tubes should not be ignored. The
discussion was not specifically about neutralization. I suggested
doubling in the final as a means to simplify the design in that
neutralization would likely be unnecessary.

73, Barry WA4VZQ


When the 6146 was used as a class C final neutralization was optional
(except maybe on 10 meters). As a linear amplifier neutralization will
lower the IMD and is a good idea for a clean signal. Most SSB
transmitters with 6146's in the final were neutralized.

BTW on 2 meters the 6146 is ABOVE it's self neutralization frequency and
HF neutralization circuits don't work. Sometimes a tuned trap in the
screen did the trick, sometimes INCREASING the plate/grid feed back with
a gimick capacitor was used. Also grounding the metal base with spring
fingers instead of the base pin at the socket might be required.

If TWO 6146's were used in push pull on VHF a conventional cross over
neutralization scheme with gimick capacitors vs the tube plates worked
out well.

  #14  
Old January 30th 11, 04:08 AM posted to rec.radio.amateur.boatanchors
Tim Shoppa[_2_]
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Posts: 9
Default Transmitter Circuit

On Jan 23, 11:54*am, Radio Vintage wrote:
I WANTED circuit for 80/40 meters CW transmitter with VFO , *2 or 3
tubes with a final valve 5933wa.
can you help me
TNX Frank


Any of the ARRL handbook "novice transmitter" circuits, spanning
several decades from the 40's to the early 70's, showing a 6L6 or 807
or sweep tube final, ought to be useful. I think every handbook had
this style of transmitter, two tubes for crystal, add a third tube for
VFO driving.

Tim N3QE
 




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