[ARC5] Vibrator Power Supplies

Fri Dec 7 18:29:36 EST 2012

The Gonset G-77 came with the power supply that was ONLY 6 or 
12 Volt DC. My original G-77A came with the AC/DC power unit. 

I have both models and recently found the G-77A power supply 
on eBay by itself. The seller obviously didn't know, but I 
notedthe small AC input connector (probably takes the old TV 
cheater cord) and also the changed rectifiers and bought it. 
Now I just have to find a cheater cord to power it up! 

Back in the day, I had a set of the twins mounted in a 1962 
Pontiac Tempest. It went into my 64 1/2 Mustang when it replaced 
the Pontiac. Then came an NCX-3 and then an NCX-5. They went 
away somewhere in the mid 1980s. The RG-9 coax was still in the 
"Stang" when I sold it 1993. 

* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* k2gkk at hotmail.com * 
* Oklahoma City, OK * 
* USAF & FAA (Ret.) * 
* * * * * * * * * * * 

> From: kgordon2006 at frontier.com
> To: ARC5 at mailman.QTH.net
> Date: Fri, 7 Dec 2012 14:46:37 -0800
> Subject: Re: [ARC5] Vibrator Power Supplies
> 
> On 7 Dec 2012 at 15:15, Robert Nickels wrote:
> 
> > On 12/7/2012 1:51 PM, GDM wrote:
> > > converted 6 volt DC car radios to AC, by feeding 6 volts AC from a
> > > filament xformer into the 6 volt primary winding
> > I've done that too for old commercial FM radios back when in the early
> > days of VHF-FM. Maybe they ran hot - but since I can't remember one
> > burning up it must not have been a problem ;-) Like a lot of stuff
> > you do when the stuff is easy to get and cheap. I'd like to
> > understand what characteristics of the transformer result in this not
> > working as expected as I wasn't aware that it was a problem.
> 
> As Sandy pointed out, the switching-frequency of a normal vibrator is 115 
> Hz.
> 
> Our power line frequency is 60 Hz.
> 
> The amount and kind of iron in a transformer is determined by (among other 
> things) the AC input frequency: the lower the frequency, the more iron is 
> required. 
> 
> Therefore, a transformer designed for an input frequency of 115 Hz would 
> have LESS iron in it than one designed for 60 Hz, and if 60 Hz is applied to a 
> transformer designed for 115 Hz, there will be a lot of heat produced.
> 
> The amount of iron required in a transformer vs the input frequency is the 
> reason that aircraft use 400 Hz power supplies: the iron required is much 
> less than 1/2 of that required at 60 Hz, and thus the weight and bulk are 
> reduced.
> 
> This is also why the Navy tried some systems at 800 Hz. They are real 
> screamers because of it too. 
> 
> If you find a transformer designed for 25 Hz AC, the transformers will be at 
> least 1/3 heavier and bulkier than those designed for 60 Hz., yet they will 
> work fine at 60 Hz.
> 
> A transformer designed for a lower frequency will generally work fine at a 
> higher frequency, but not always.
> 
> Others here can tell you exactly why all the above is so. It has to do with the 
> "support" the magnetic field needs, and that is dependent on frequency.
> 
> > One commercial ham rig I am aware of, the Gonset G-77, was a two-part
> > unit with the very small (by 1950s standards) RF unit under the dash
> > and the modulator and vibrator power supply in a separate box (in the
> > trunk, normally). They sold two power supplies that were identical
> > except for one thing: one just had the DC input for operation from
> > vehicle batteries, and the other had an additional primary winding so
> > it could run from DC or AC by simply plugging in a cheater-type cord. 
> > I had one of the former before trading around to get one of the
> > latter, and it works great. But maybe there are some changes to the
> > transformer that I'm not aware of.
> 
> Yes. It probably was designed to operate from 60 Hz, and since a HIGHER 
> frequency will work fine in a transformer designed for a lower one, they could 
> easily use the same transformer.
> 
> There are also Handbook vibrator-power supplies that were designed the 
> same way: to use DC through a vibrator, or 110 VAC 60 Hz. input, 
> depending on how the jumpers were set, and they used 60 Hz transformers.
> 
> Ken W7EKB
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