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Message-ID: <3.0.1.16.20010228102047.2cdfe722@mail.cc.kuleuven.ac.be>
Date: Wed, 28 Feb 2001 10:20:47
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: RE: Icom IC-746 on LF
In-reply-to: <65AECDF1F89AD411900400508BFC869F0D75EE@pdw-mail-1.dera.gov .uk>
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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:w1jhj@netzero.net]
>> Sent: 2001-02-27 18:43
>> To: rsgb_lf_group@blacksheep.org; lowfer@qth.net
>> 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
>> http://geocities.com/ws1k.rm
>> 
>> Shop online without a credit card
>> http://www.rocketcash.com
>> RocketCash, a NetZero subsidiary
>> 
>
>
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