[ARC5] A simple receiver improvement

[Glen Zook]

The Hammarlund receivers, up to, and including, the HQ-150 (also includes the HQ-100 and HQ-110 which are later receivers) have balanced antenna inputs up to 600-ohms and the baluns should definitely help.  The HQ-160 has an antenna impedance of around 75-ohms unbalanced and the HQ-170 series and HQ-180 series have an antenna impedance of 100-ohms balanced / unbalanced (depends on if the A-2 terminal is connected to ground).  With those receivers, using a television balun probably wouldn't do much good.
 
Glen, K9STH


Website:  http://k9sth.com



On Tuesday, January 14, 2014 3:35 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
 
On 14 Jan 2014 at 12:56, Ian Wilson wrote:

> Ken,
> 
> In principle you could just use an L-network or something to couple
> more energy from the antenna to the tuned circuit of the first RF
> stage. However .. this will reduce the selectivity of that tuned
> circuit, so you may run into diminishing returns.
> 
> 73, ian K3IMW

That is an idea.

However, I looked up some balun design math.

Z2 = n^2*Z1

where n = the turns ratio, Z2 = one impedance and Z1 = the other.

n in this case turns out to be about 4.4

This means that one would wind 5 turns on the "primary" side, and 22 turns 
on the secondary side to achieve a 50:4.1K balun.

Now I have to figure out which mix of toroid I would have to use.

This seems do-able and small enough.


Ken W7EKB
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