Topband: TopBand Receivers

[Tom Rauch]

Hi Riki,

> My comments about practically identical weak signal characteristics for
> the 3 receivers (R4C, FT-1000D & Omni 6+) were not laboratory tests - they
> were actual on the air tests with the possibility of instantaneously
> switching between the receivers (one pair at a time). I've not noticed any

I wouldn't expect you to notice much difference, unless you had 
one or more very strong signals close to the operating frequency.

The R4C is generally a little better than most receivers on days of 
strong QRN that has gaps in the noise, because the fast AGC in 
the Drake is many times faster than the FT-1000 AGC and other 
AGC systems.

The Drake AGC isn't good, it has overshoot, but the redeeming 
quality is the speed. It is fast enough to recover between noise 
bursts without loosing unnecessary amounts of signal.  

> degree of phase noise in my FT-1000D which was purchased new in Winter
> 1998.  Please remind me how to look for this "gremlin" in a practical (on
> the air) receiving test, and I'll try again. 160M can get quite lively and
> congested here during contests (many Europeans) - but I'm not sure if the
> signal levels reach those that require the extremely high dynamic range
> that you're talking about.
 
Here in the US, with a dozen first-hop signals at 40 over 9+ a few 
hundred Hz apart, synthesizer problems show up. It appears as a 
hissing signal sometimes with a bit of a buzz, and can extend 
many kHz in some cases. It affects both the transmitter and 
receiver.

You can only pin the fault down by having a very clean test 
oscillator to listen to, or a receiver known to be clean. If you hear 
synthesizer noise it is almost impossible to tell if it is in your 
receiver or their transmitter. The Drake has virtually no broadband 
oscillator noise, and the Ten-Tec is really good also (but lacks the 
dynamic range of a modified Drake).

I suspect this is only a problem in congested areas of activity, like 
the USA and Europe.

My 1000(D) is reasonable but not exceptional. Phase noise is 
mostly a problem running two transmitters here at the same house 
on the same band. The 1000(D) is 10-15dB worse than my 751A, 
and far worse than a Drake (which has no detectable phase noise). 
A TenTec Omni 6 plus was between the Drake and 751A in phase 
noise. FT1000MP's seem to run the range of "horrible" to about the 
same as a 1000D.

I'm hoping the new 1000MKv is improved in the synthesizer noise 
area. Unfortunately it mainly affects 160 meter operation in 
congested areas (because so many signals are so loud), so the 
problem may be ignored.


 
73, Tom W8JI
w8ji@contesting.com



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