[Elecraft] Duplicating the KPA100 LP filters

[Geoffrey Mackenzie-Kennedy]

Vicd Rosenthal wrote:

> I'm thinking about duplicating the KPA100 LP filter section so I can use 
> this amp as an output stage for another rig.  This sounds like a 
> no-brainer, but I wonder if there's any reason not to do this?
>
> Also, does anyone know the manufacturer and model number of the relays 
> (K3-K12) that Elecraft used?  I would have to take my KPA apart to look!

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Hi Vic,

My KPA100 purchased in early 2003 uses OMRON type G6E - 134P - ST -US relays 
for K3 - K12 (and K1, K2).  Unless I'm mistaken the contact rating is 0.4A @ 
125VAC  or  2.0A @ 30VDC which seems to be a bit 'light', but no problems so 
far.

My KAT100, same vintage, uses HASCD  KL1TC 12DC12 relays for K1 - K18, 
contacts rated at 12A @ 28VDC. This rating is typical for use at 100W HF RF 
with a good safety margin.

I would strongly recommend that you include a lowpass filter between the 
KPA100 filters and your antenna tuner (or antenna if no tuner is used), 
whose cutoff is around 32 MHz.  HF  LP Filters including  the type used in 
the KPA100, especially when densely packaged, can exhibit 'peaks' of low 
attenuation at VHF and UHF upwards. Toroidal coils do talk to one another to 
some degree.

73,
Geoff
GM4ESD