[ARC5] My ARC-5 station on AM.

[Kenneth G. Gordon]

On 22 Feb 2015 at 19:44, Jim Wiley wrote:

> If you are thinking of the Eico 730 modulator,

Yes. Exactly. My memory is a bit foggy. That is exactly what I meant: the 
Eico 730.

> it was a 50-watt audio output
> unit.

Oh. I didn't remember that.

>  I used one for a while in the early '60s, plate modulating a severely
> hacked DX-40.  Worked well.

Yes. I understand that the Eico 730 is a good unit. I also liked my 
DX-35....except for the power transformer...

> The only thing left of the original DX-40 was the basic RF circuitry.  Power
> supply, modulator, and VFO all were external.
> 
> The DX-40 had suffered a transformer failure,

...which was not even remotely uncommon: I lost two power transformers in 
my DX-35 within two years of my building it in 1956. 

After the second one, I replaced it with a much more robust one, torn from a 
console TV set, and used that "Economy" connection. 

I also got rid of that really stupid "stacked" connection of the oscillator and 
buffer stages and went to straight parallel feed for both stages. 

After replacing that equally stupid moving vane meter with an "expensive" 
Simpson D'Arsonval meter, I used that rig for many years afterwards without 
any further trouble. I normally ran it at 90 watts input.  I worked the world with 
that rig. Wish I still had it.

I even used it on RTTY, driving a modified BC-610E (304TL final) to a KW.

I drove the DX-35 with a rebuilt VF-1, modified for "shift-pot" FSK. The VF-1 
was unusually stable.

> so I built a complete
> substantially more robust external power supply with regulated B+ for the
> oscillator/driver stages.   I used a HG-10 VFO,  the Eico 730 modulator, and
> rack-mounted the whole thing.

That sounds REALLY neat! :-) I wish you had a photo or two of that.

>  Ran the poor old 6146 PA tube rather harder than
> it was designed to do,  approximately 100 watts DC input (plate modulated AM) 
> to the single tube, but it never quit.   Finally scrapped it out when I moved
> to Alaska in 1963.  

Ah, too bad.

> It was my "high school" rig,   paired with a Hammarlund HQ-150 receiver, set
> up in the attic of my parents home in California.

Well, I am impressed, Jim. Very interesting. Thanks for sharing.

Ken W7EKB