[ARC5] Another one - 10 meter BC-454

[John McCarty]

O.K, so it's not a BC-454, it's a R-26, but it suffered the same fate.

It's a later R-26 I would guess because it has multi-colored vinyl 
looking insulated wires. Made by A.R.C.
I picked it up some time ago, don't remember where. Whoever did the hack 
was making a 10 meter mobile
rig. Usual mods, antenna connector relocated to the rear deck and 
changed to a Motorola car radio antenna
jack, controls on the front, filter inductor and bfo coil gone, output 
transformer replaced. Brass shim stock pieces
added to make the tube cover fit tighter. I have to hand to the guy, he 
re-did the tuning dial, white paint on a black
dial with a "quaint"  look. It was hand drawn by a steadier hand than 
mine. A broad white line high lights the
phone bands. But the really cool part is an added dial light made from a 
30-30 bullet.

I hadn't done anything with this poor victim since it come home with me, 
so I fired it up, couldn't make it worse.
Looks like it was powered from the rear 7 pin connector, so I followed 
suit.12 volt battery for the filaments,
120 vdc from an old homebrew supply that had been cobbled together back 
in the 70's to power a Type 12.
Since I don't have a 10 meter antenna right now, I hooked it up to my 6 
meter vertical dipole.
No smoke and a gentle hiss from the head phones. Antenna trim had no 
effect. Tuning down to the 27Mc
end of the dial made the front end go into oscillation. The antenna trim 
could stop/start the instability. Since
holes had been drilled in the top of the case to gain access to those 
trimmers, I couldn't help myself but tweak.
Maybe the trimmers were just corroded but with just a little budge, I 
was rewarded with a big increase in back
ground noise and now the the noise could be peaked with the antenna 
trimmer. Fooling around with the
trimmers I was able to get the front end to track better it would seem 
and most of the instability is gone. But
it appears that the gain rolls off above 29.4Mc

10 meters seemed to be dead by the time I got the set going (6PM CST), 
but 11 meters was rockin' and rollin'.
Seems like it's the same voices from 30 years ago. Since this poor pup 
has been abused beyond reasonable
redemption, (did I tell you half the dynamotor mounts were gone?) I 
think I keep it like it is, maybe re-cap it when
I get time. Maybe I'll use it to back up my 6 meter Ameco nuvistor 
converter.


73


John n9hrt

















On 2/5/2013 8:11 PM, Kenneth G. Gordon wrote:
> Today, I measured the gain through the RF amp using the formula, DB=20log V1/V2
>
> I get 19.3 DB gain, which seems reasonable.
>
> 0.035 VPP input results in a steady 0.325 VPP output.
>
> Gotta check the maintenance manual to see if that really is OK.
>
> Ken W7EKB
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