Hello group,
Most HF-rigs have a "push-pull" PA that has an input and output
transformer. It are most likely these transformers that determine the lower
frequency limit.
I believe to have read an article in CQ-DL about the first 136kHz
transmissions between DA0LF and DA0VLF in Friedrichshafen (1997 ?). One of
the stations used a 100W HF push-pull PA to get 20W on 136kHz and they
needed a fan, not to cool the transistor but to cool the output
transformer. So even if you get your HF rig running on 136kHz I suggest to
limit the output to a few Watt in order to avoid a 'meltdown' of the output
transformer.
73, Rik ON7YD
At 08:43 28/02/01 -0000, you wrote:
I don't know those particular mods, but my IC746 was supplied (quite
intentionally) with all band transmit capability. However, the
transmitter is still inhibited when trying to operate below 1.5MHz as
the PA cannot cope below this frequency. Presumably the MARS mods you
mention only require transmission at a few other HF freqs so the 100kHz
lower limit could be a misunderstanding / typo on the authors part.
The firm supplying it told me in no uncertain terms that the guarantee
was only valid for transmission in the amateur bands, but Icom confirmed
the rig is quite happy transmitting over the whole HF spectrum, but
trouble would come if trying to transmit in the 30 - 45MHz region as it
would still be trying to use the 30MHz low pass output filter. Also VHF
transmission much outside 140-150MHz would cause problems, again due to
the output filter.
Andy
-----Original Message-----
From: Jonathan Jesse [mailto:[email protected]]
Sent: 2001-02-27 18:43
To: [email protected]; [email protected]
Subject: LF: Icom IC-746 on LF
While surfing around the "net" for specifications on Icom's
IC-746 HF/VHF
transceiver, I found a modification to open the transmit
capabilities (so
called MARS/CAP mod). Reading on, I found that the author
stated that this
mod will open the transmit from 100khz to 60mhg. 100khz?
Has anyone tried
and or confirmed this?
Thanks,
Jon W1JHJ
Jon
W1JHJ
Plymouth, MA
FN41qw
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