[Hammarlund] HQ140 - really *LOW* sensitivity

[Kenneth G. Gordon]

On 16 Jan 2013 at 12:10, Bill Breeden wrote:

 
> Bob,
> 
> Don't know what kind of antenna you are using, but all of the
> Hammarlunds that I have owned have a balanced antenna input with three
> terminals on the antenna terminal strip.  The terminal strip on my
> HQ-145 is marked "A", "A", and "G" from left to right.  If you are
> using any antenna other than a balanced antenna with a balanced feed
> line, a short jumper or strap should be used to connect the center "A"
> and right hand "G" terminals together.  I often use a random single
> wire antenna on the left "A" terminal and the jumper between the other
> "A" and "G" makes all the difference.
> 
> 73,
> 
> Bill - NA5DX

Bill: You are absolutely correct. When I was aligning my HQ-110C a long 
time ago, I found the sensitivity on 160 meters to be VERY low when 
compared to the other higher bands. I was mystified.

When I finally looked closely at the schematic, and did as you suggest 
above, the sensitivity on 160 jumped to the same as it was on the other 
bands.

The RF input on the HQ-110C is a link. If one side of that link is left open, 
sensitivity falls way off. A doublet antenna works fine. For any sort of 
single-wire antenna, the A terminal nearest the G terminal MUST be 
connected together, and this includes coax, if used.

My HQ-110C had had an SO-239 added by the previous owner and that was 
jumpered directly to the "open" A terminal.

Since the input impedance of the HQ-110C, and probably other 
Hammarlunds is pretty high, one can sometimes use one of those 300 ohm 
to 50 or 75 ohm TV "matching" transformers between the receiver and the 
antenna. In many receivers, this makes a big difference. In others, not so 
much.

vy 73,

Ken W7EKB