From: "Hans-Joachim Brandt" <hajo.brandt.dj1zb@t-online.de>
To: rsgb_lf_group@blacksheep.org
References: <3.0.1.16.20010228102047.2cdfe722@mail.cc.kuleuven.ac.be>
Subject: Re: LF: RE: Icom IC-746 on LF
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Date: Thu, 1 Mar 2001 01:38:36 +0100
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Dear all,

concerning the beginning of LF amateur operation in Germany I must confess that 
a very detailed description of the equipment used has never been published but I 
think that the contribution below by ON7YD should be corrected:

Just before the Ham Radio Fair at the end of June 1997 at Friedrichshafen our 
administration had isssued two provisional licences for DA0LF (Peter Bobek, 
DJ8WL) and DA0VLF (Dr. Hartmut Buettig, DL1VDL, DARC HF manager) for a 
transmitter power of 100 watts (now we still have 20 watts nominal only). Time 
for preparations were very short, nobody could even think of a 100 watts PA. For 
DA0LF Peter Bobek employed his Hagenuk receiver and exciter with an output of 
200 mW to a random wire. For DA0VLF "Hardy" Buettig had prepared a 20 watts PA 
and a loop aerial, but could not contribute anything for receive and for driving 
his PA. Therefore he was very glad that I could supply him with a passive LF 
converter to 14 MHz (then used with a TS-50 behind, showing 14.136.6 on the 
dial) and a crystal mixer exciter which produced just 3 watts output when 
combinded with Hardy's PA. Coupling between the random wire and the LF loop even 
within the same exhibition hall was rather poor, but a few meters of wire 
connected to the loop did not detune it but improved reception on both sides 
considerably. RST had been about 579. At the stand of the DARC HF referate a lot 
of visitors took the chance to have a first qso on LF and to receive a special 
QSL card.

I myself could not travel to Friedrichshaven that year, because my third son had 
decided to marry just on Friday of that weekend!      

In another cq-DL article (5/1998) Peter Bobek reported that to increase his LF 
power to 50 watts for his long-range qrss tests he had used a push-pull power 
amplifier with two MRF454 employing "completely inadequate cores for LF". This 
may have been the PA needing more cooling for the output transformer than for 
the transistors. 

73 Ha-Jo, DJ1ZB


Rik Strobbe schrieb:
> 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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> >
> >
>