On 26-5-2012 16:36, Stefan Schäfer wrote:
Yes, the relais, this is what i am doing in all my HF PAs as well. I
have a RX/TX relais that is bypassing the PA in RX mode.
It is switched automatically, detecting a input signal on the right band
(using a small band pass filter) and then switching to TX.
It is fast enough so that a "dit" in CW at 120 BPM can still be
detected. So, it is quasi full-BK mode. A delay time for releasing the
relais can be adjusted by a pot.
==== TS440 has a build in relay for this purpose, the user has only to
activate it. In those days it was designed to operate it with AMTOR so
it's vy fast.
Stefan Schäfer wrote:
A mixer for receiving? How do you receive on MF?
==== TS440 considers 0,5-1,6MHz as broadcast. For this band an
additional attenuator is inserted. If you by-pass it and having a nearby
BCST stn all kind spurs will be generated.
Think some ICOM sets have the same arrangement.
I removed this attenuator but having a local AM station nearby it added
more noise, so left the system in it's original state.
Moving to the new QRG means that the TS440 will release the BCST
attenuator, so the S-meter will move up.
Stefan Schäfer wrote:
The LPF in my PA actually is a BPF so i will have it in series to the
RX. That will be a very good first preselector...
==== For 500 I use a small and simple bandpass filter which I "lurked"
from PE1GRL,
http://pe1grl.khds.nl/500kHz/rxtxbfsch.png
In his turn he adapted it from yu1lm
http://yu1lm.qrpradio.com/BP-LP%20filters%20for%20LF%20%20and%20500kHz.pdf
This really cleans the signal from unwanted spur.
View the local noise level is rather high here, there is no particular
need for a very sensitive receiver. It's becoming worse every day anyway.
For RX I use the TX antenna fully tuned. E-probe is also available but
just 2m away from the 35m L-antenna. E-probe coupled strongly on the
L-antenna.
It is more acting as a buffer amplifier.
Stefan Schäfer wrote:
I still have no concept. Of course there are many but i have no decision
so far. Yes, a simple DC receiver is my favourite as well. The IC-706 is
an option but not quite /p (takes 1.5A in RX mode!).
My K2 doesn't work there i am afraid. So i will need a converter.
==== The receiver here is just the TS440 direct. TX in split mode.
PE1GRL used a modified 160m Softrock. Modification details on his
website http://pe1grl.khds.nl/500kHz/500kHz.htm#_softrock
Maybe SoftRock type is an option when /P.
FYI PE1GRL mainly worked /P with a kite aerial. The moments he was QRV
in WSPR he was vy strong in EU.
Jan/pa3abk
--
pa3abk<-> dordrecht jo21it
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