to what do you attribute the reduction in output power?
Is it gate capacitance acting like a low pass input filter to the IRF510,
or is it drain capacitance, or something else?
would be appreciative of better understanding....]
gordon
________________________________________
From:
[email protected] <
[email protected]> on behalf of Jose Amador <jose.co2ja@...>
Sent: Saturday, October 28, 2017 7:32 AM
To:
[email protected]Subject: Re: [BITX20] Multiband bitx G6LBQ links
The IRF 510 works up to 10 m, but from 4 watts on 40 m goes down to 1
watt on 10 m, that is the cost of a simple solution, discovered while
using a Genesis G-40, a kit made out of the YU1LM's AVALA. A flat,
broadband amplifier would be better, but that is an more modified BitX.
Jose, CO2JA
El 28-Oct-17 a las 06:28 AM, John Backo via Groups.Io escribi¨®:
Smitty:
Yes; it can be done.
Check each and every band for birdies.
Check out the HRI DDS v.4 for a dual mcu DDS
that uses the second mcu to control bandswitching.
You will have to modify that for the Si5351 instead of the
AD9850 for the DDS. But you are not alone.
With the present BITX40 board configuration, it is unlikely
that the IRF510 will go very well above 17m or so.
Figure out a layout with a separate PA and relay controlled
LPFs. The BPF configuration is much simpler...probably
one or two circuits will do.
Check out the Minima and uBITX designs to see what problems
have already been run into...designing a multi-band superhet is
not exactly simple. There are a lot of variables.
But it can be done with a BITX40 board as the basis. Go for it.
Build and MEASURE; work with blocks that fit together for a whole.
The easiest thing to do is design everything with a 50 ohm in/out
impedance. Then everything matches.
john
AD5YE
