The lower the resistance the better the design has to be otherwise the R
gets smoked. 50 Ohms seems to be a value that most can get working without
bothering to open a book.
The lower the R the broader the bandwith of the suppressor so 10M burnout
becomes critical especially with 811/572B's whose parasitic is around 75
MHz. Thats one reason why few can get them to work well on 6M.
Remember that the purpose of the suppressor is NOT to dissipate the
parasitic power but to stop it forming in the first place.
Measures voodo has zero engineering behind it and is strictly brute force.
Try some key down power measurements in a SB-220 or larger amp on 10M, the
nichrome starts to glow. The difference in power between a real suppressor
and voodoo is over 100W.
Carl
KM1H
----- Original Message -----
From: "DAVE WHITE" <mausoptik@btinternet.com>
To: <amps@contesting.com>; "Jim Thomson" <jim.thom@telus.net>
Sent: Friday, July 16, 2010 1:40 AM
Subject: Re: [Amps] 2 x 4-1000 supressor.
I have no idea if there's supposed to be a specific value of resistor - but
50 ohm carbons was what I had at the time (I bought a boxfull at a hamfest
fleamarket!) and they looked a bit weedy - so the (non-scientific)
suck-it-and-see approach was to put "a resistance" in there. I did think of
three sets of three in parallel connected in series but it just seemed
clumsy and I thought I'd try it with the one set. It worked so I left it
alone.
Is there anything special about 50 ohms?
Dave G0OIL (The fellow from G land....)
--- On Fri, 16/7/10, Jim Thomson <jim.thom@telus.net> wrote:
From: Jim Thomson <jim.thom@telus.net>
Subject: [Amps] 2 x 4-1000 supressor.
To: amps@contesting.com
Date: Friday, 16 July, 2010, 1:46
Date: Thu, 15 Jul 2010 17:45:32 -0500
> From: Rob Atkinson <ranchorobbo@gmail.com>
> Subject: Re: [Amps] parasitic suppressor voodoo
> On Thu, Jul 15, 2010 at 3:00 PM, Carl <km1h@jeremy.mv.com> wrote:
>> Agree with Dave. In the past I turned out many 1-2 holers grid or cathode
>> driven to order; most covered 160 or 80-10M. Then I used 20-25W Globars
>> or
>> surplus 68 Ohm 50W Carborundums which I bought almost 100 in sealed
>> packages
>> for real cheap.
## whoa. The fellow from G land is using THREE 50 ohm resistor's in parallel
= 16.67 ohms.
KM1H is using a 68 ohm -50 w globar. Carl, are did u use a SINGLE 68 ohm
resistor ??
## On my single and 2 x hole 4-1000's from the 70's.. each suppressor
consisted
of 5 x 250 ohm resistor's in parallel [ 2 watt carbons]
## If I remember correctly, any combo that totaled aprx 50 ohms worked good.
## Later on, I tried using a SINGLE 20-25 watt, 50 ohm globar, and that
worked good too.
## whether 2 watt resistor's or globars used, in all cases, cu strap was
used , [ 2- 2.5 turns]
## They were all 80-10m amps... no 160m. Back then, we were still only
allowed 25 w on 160m, and
loran stations were super loud. Forget when the loran was shut down. While
the loran was still on,
160m was just a mess of 30-40 over S-9 crud.
>> Stopped that when all the local AM stations used the tubes until they
>> were
>> even almost dead as modulators or went SS. I did about 10 3CX3000A7's and
>> a
>> few 4CX5000A's after that.
### watch out. Some folks on here will read you the riot act.. abt 'ethics'
, the 1.5 kw
limit, and other nonsense.
later.... Jim VE7RF.
>>
>> Carl
>> KM1H
>>
>>
>> On a 2 times 4-1000A amp (5.5kv, grounded grid, cathode driven) I used
>> two
>> separate parasitic suppressors, each with 3 paralleled 50 ohm carbon
>> resistors inside a 15mm diamater two-turn coil of 2mm copper wire over
>> about
>> 10mm length. The amp has worked flawlessly (80 thru 10m) for many years.
>>
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