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Dear forum,
I have read somewhere from the posting messages that the output of pre
driver should be about 300 mWatts,
but I read from the article it should be about 300 mVolts.
Which is right ?
-------
I begin to test the tx section,
rx section test is good in 3.5; 7; 10; 14 MHz.
-------
Thanks.

Based on my proto 300mW is correct. If there were 300mV the power
would be about 2mW which is way to little.

Allison
KB1GMX

Hi Milarepa,
based on my measurements, it is only a few mw, so the oposite of
what Allison measured.
I searched for you in the older postings (I have often the feeling
that older messages are not red) and you can find my answer in
message 375 (containing a mistake) and 387.
Good luck,
Chris.

--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:

Based on my proto 300mW is correct. If there were 300mV the power
would be about 2mW which is way to little.

Allison
KB1GMX


--- In BITX20@..., "MILAREPA" <MILAREPA@T...> wrote:

Dear forum,
I have read somewhere from the posting messages that the output

of pre

driver should be about 300 mWatts,
but I read from the article it should be about 300 mVolts.
Which is right ?
-------
I begin to test the tx section,
rx section test is good in 3.5; 7; 10; 14 MHz.
-------
Thanks.

Hi,

2mw is very low from the driver. Mine I see nearly 1mw at the output
of the bandpass filter (L1, L1,L3). The driver stage brings that up
to near 300mW on mine. I don't use the IRF510 as the output is more
than sufficient to drive a TenTec 1208 transverter at 100mW,
1mW however was not adaquate. Driver transistor used on mine was
2N2219A with bifilar transformer wound on a 2 hole core of -43
material to match 50 ohms. Without the 5db output attenuator it
measures as 3.8V rms across 50 ohms which is actually 288.8mW using
a HP rf voltmeter. Thats close enough to 300mW.

If you are using a trifilar transformer on the driver and measure
the power to the IRF then the driving impedence is around 10-12 ohms
and a 50ohm power meter will be inaccurate. Even then I'd expect
to see about 1.7-1.9V of rf at that point.

In any case 300mV is invalid. The gate of IRF needs to be driven
with several volts of RF to develop expected power without instability.

On mine the Q14 (predriver) device is 2N2222A and driver is 2N2219A
both have FT ratings of 350mhz which is adaquate to get good gain at
14mhz.

Measurements at the output of the filter (at 50ohms) is .9-1mw.
After Q14 I get 40mW. Adding the driver brings that to 300mW.
I used ferrite loaded transformers at T1, t2 and T3 as well as
collector of 2n2219A. Also added a choke coil (DC return) at RF
mixer (100uh molded type) and at modulator. Transistors used
are Q1,Q13,Q7 are 2n2222A, Q2,3,12,11,9,8,10 are all 2n3904.
This version uses a different VFO (Hartly with fet buffer).
All circuits are bypssed with more than shown is schemtic
and some sections are shielded (modulator and bfo). Construction
is dead bug (ugly on ground plane OF unetched PCB).

A newer version is being built that will use a PLL to provide LO
and the output will be for 6m using 9.6mhz filter, 40mhz LO and
I may try commercial DBM (anzac MD108) for both modulator and
mixer. Since this one is to be small power will be limited to
around 3-5W and use a RF transistor 2sc1971 for the final.

More information than asked for but, measurements are how I know
a circuit does indeed perform as expected.

Allison