Topband: Re: topband RX

[Tom Rauch]

> Given the RX antennas I'm going to be using, I'm 
> actually going to have to add preamplifiers to 
> them!

I use push-pull CATV bipolar transistors in preamps, and the 
minimum gain necessary to work with my least sensitive receiver.

One way you can test a system is to switch from the antenna to a 
dummy load placed at the antenna terminals that has the same 
impedance as the antenna. Do this at the most quiet time you 
expect to ever use the system! Don't do it at night during the 
summer, or when insulators are arcing in your area! 

You should have an easily heard decrease in noise level when the 
swap is made. You can always pad the system or switch out 
amplifiers on noisy nights if overload becomes a problem.

If overload isn't a problem, the extra gain won't hurt. 

> I always thought my IC-735 was a nice (but not 
> great) radio until I started trying to listen to 
> DX on 80 and 160.  It was nearly useless.  
> Switched to using a Drake R-4B and suddenly I 
> could hear.  The problem was PLL phase noise in 
> the Icom.  Not fixable with external anythings.

My IC751A is 10-15 dB better on phase noise than my FT1000 and 
a FT1000MP! The Ten-Tec Omni 6 plus I had was much better than 
the ICOM. None were as good as the Drake PTO scheme, which 
IMO is ALL the R4C has "going for it" when stock. That's why so 
many people are disappointed when the get an R4C, and don't see 
any change over their transceiver. 

R4C S/N's below 18700 or so (MOSFET mixer instead of 6BE6) 
are very poor competition receivers, and take hours and hours to 
fix. The other R4C's are acceptable with only a 600Hz Sherwood 
roofing filter added for CW. A wider filter won't help a thing, for CW 
use.

73, Tom W8JI
w8ji@contesting.com



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