[UK-CONTEST] What is the best VHF Radio
John F Wilson
UK-Contest at grebe.plus.com
Mon Sep 8 10:29:56 EDT 2008
Neil,
I reckon the IC7400 despite one or two issues, is hard to beat, on all
round performance, strong signal handling and trasmit noise close to
carrier. The problem is that it only covers HF, 50 MHz and 144 MHz.
Its high time ICOM produced a DSP VHF/UHF rig as a successor to the
IC910 but I suspect they won't due to the smaller market than for HF rigs.
On your original point, my feeling is that with the attenuator in and
the preamp off, it was the transmitted signal that was at fault unless
you just turned your preamp off by removing the supply to it without
switching it out of circuit in which case it might be that if the signal
was strong enough it could still be driving the off amplifier device
into non-linearity.
73 John G3UUT
Ian Burns wrote:
> Neil,
>
> The Javornik II can be found here
>
> http://lea.hamradio.si/~s53ww/xvrt/xvrt.htm
>
> The page also shows some screen shots of the transverter o/p indicating
> why you don't want to use it. With the PA turned off, depending on the
> drive control setting (anything over about 1/4 is bad) the o/p has
> spurii about 45dB down from the main carrier. These spurs move in and
> out with respect to the main carrier as the rig is tuned across the band
> and are offset anywhere from zero to several hundred KHz from the
> carrier. Filtering is not an option.
>
> When you have seen how bad the TVTR o/p from the FT1000MP is you won't
> want to use it to transvert to any band...
>
> As Jiri says a pad on the main o/p works well and is clean.
>
> 73
> Ian
>
>
> G3RIR wrote:
>
>> Ian,
>>
>> Thanks for the response. I have never heard of Javornik perhaps you can let
>> me have a link.
>>
>> I have an FT1000mp as well as my FT847 and have a DEM transverter for 432
>> which was used with the FT1000mp. I moved to the FT847 for contesting on 432
>> as there are not too many very strong signals on 432 from our NFD location
>> (G3SDC/P on the Norfolk coast (JO02st)) and it is much more convenient and
>> smaller that the FT1000mp etc!!
>>
>> I have recently been active on 144 and that is where the FT847 might not
>> have a robust enough receiver. However I found only one signal splattering
>> during the weekend from my home qth in IO92 so I am not blaming the rx just
>> yet.
>>
>> What did you find wrong with the FT1000mp transverter output? Could it be
>> cleaned up with filtering? When using the FT1000mp for a transverter I
>> switch off the pa completely from inside the little top lid as this is safer
>> than someone accidentally running too much power from the pa into an
>> attenuator.
>>
>> Neil, G3RIR
>>
>>
>> -----Original Message-----
>> From: uk-contest-bounces at contesting.com
>> [mailto:uk-contest-bounces at contesting.com] On Behalf Of Ian Burns
>> Sent: 08 September 2008 09:13
>> To: uk-contest at contesting.com
>> Subject: Re: [UK-CONTEST] What is the best VHF Radio
>>
>> I can thoroughly recommend the FT100MP and Javornik II transverter
>> combination. The receiver is not totally bomb proof but is noticeably
>> better than my FT847. We used the setup at G0FBB in the 2m trophy this
>> weekend and had no real problems despite some very loud signals on the band.
>>
>> The only drawback of this combination is that the transverter output of
>> the FT1000 can be too dirty to use on a crowded band. It's a fair way
>> off the VHFCC recommendations of -100dBc... The main o/p is clean enough
>> to use via a suitable attenuator though.
>>
>> 73
>> Ian.
>>
>> Dave wrote:
>>
>>
>>> At 20:21 07/09/2008 +0100, G3RIR wrote:
>>>
>>> There is a useful comparison of HF Tcvrs here
>>> http://www.df9ic.de/tech/trxtest/trxtest.html
>>>
>>> 73 Dave G4RGK
>>>
>>>
>>>
>>>
>>>> Earlier today I reported to a station on 144MHz that his signal was very
>>>> wide. I could hear splatter about 12kHz either side of his signal.
>>>>
>>>> I turned off my mast-head pre-amp, switched in an attenuator and turned
>>>>
>>>>
>> my
>>
>>
>>>> beam side on so that I only had s7 registered on my s-meter. The splatter
>>>> was still noticeable.
>>>>
>>>> The station concerned said he was definitely not over-driving anything.
>>>>
>>>>
>> He
>>
>>
>>>> asked what receiver I was using and on being told it was an FT847 he
>>>> suggested that it was my receiver at fault. This may of course be the
>>>> problem but he wasn't the only loud signal on the band but was by far the
>>>> widest.
>>>>
>>>> What are the group members' views on the FT847 in handling such
>>>>
>>>>
>> situations
>>
>>
>>>> and indeed what is the best receiver around for 144 and 432?
>>>>
>>>> I am also interested to know what is the specified noise figure for the
>>>> FT847; of course the manual only refers to sensitivity!
>>>>
>>>> Neil, G3RIR
>>>>
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>>>>
>>>>
>>>>
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