[Heath] Need info.............

[Kenneth G. Gordon]

On 25 Jun 2011 at 9:42, Jeramy Thibodeaux wrote:

> I can see where the confusion comes in as this part number has been
> assigned at least two different values.
> 
> SB-220 Amplifier
> Part Number 45-78 is listed as 9uH RF Choke
> 
> HL-2200 Amplifier
> Part Number 45-78 is listed as 10.3uH RF Choke
> 
> This does make me wonder where else this part number was used and I
> don't even want to speculate how this happened but it does create a
> dilemma.

It is well known that the inductance value of the original filament 
choke in both the SB-220 and the SB-200 were actually a bit too low 
for effective "choking" at 80 meters. Part of the drive signal is 
lost before it gets to the final amp tubes.

A substantial increase in output on 80 meters (or reduction in 
necessary drive signal levels) can be achieved by simply winding and 
installing a new, "larger" (more turns) filament choke on an 
appropriate ferrite rod.

If one wishes to add 160 meter capability to either amp, one MUST do 
this (among other things).

I would guess that Heath increased the value of that choke for the HL-
2200 since this problem had been recognized by then.

Then they used the same part number so that users of the earlier amps 
who needed a replacement choke would enjoy the increased output on 
80.

I know that Heath did similar things in the past.

Ken Gordon W7EKB