[CQ-Contest] "IR" cans update

Clive Whelan clive at gw3njw.fsworld.co.uk
Sun Sep 9 00:57:35 EDT 2001

Thanks to everyone who responded both here on the reflectors and 
via email.

It looked pretty positive, so I took the plunge and bought a 
pair of 863Mhz cans. These are made by Thomson, come with 
rechargeable batteries and have a sensitivity of 107dB/mW, 
pretty important for use with the FT1000MP which is rather deaf 
on the audio side ( cans not speaker).

That's the good news, now the bad news. It seems they are 
virtually useless for the purpose intended. What seems to be 
happening is that the input stage of the base unit is being 
overloaded even at quite low audio inputs. The practical effect 
of this is akin to using a Rx with no, or at least defective 
AGC. On a quiet band with few signals there is not much of a  
problem, but as soon as a strong signal is received, the things 
are  blown away and distort the audio horribly , or at best 
flatten the response. The above refers to the FT1000MP, and on 
the TS930S( which has gutsier audio) the situation is even 
worse. I did suspect the unit was faulty or perhaps the Nicads 
were not properly charged.The latter was quickly eliminated, and 
when the unit is hooked into my Sony mini HiFi system, the cans 
work perfectly, with no hint of distortion or overload at 
maximum volume setting. I wouldn't call the repro. really high 
fidelity but it is perfectly acceptable. When using the FT, the 
same effect occurs even if the ext. speaker, or AF out ( 600ohm) 
jacks are used.

This is really a puzzle to me, and I confess I don't know what's 
going on. It occurs to me that perhaps a resistive pad on the 
input might help, but my best guess is that the problem is too 
severe for such a simple remedy.

So it looks like I have a nice set of remote cans for my HiFi, 
but not for the contest station; hey ho.

N.B. that this is not a request for help, more a caveat emptor 
call to those with similar aspirations. It goes without saying 
however, that all suggestions are gratefully received.


gw3njw at gw7x.org
Contest Cambria-http://www.gw7x.org

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