>
>
> Date: Fri, 15 Jan 2010 09:17:21 -0800 (PST)
> From: Radio WC6W <wc6w_amps@yahoo.com>
> Subject: Re: [Amps] (Perhaps) A plate choke too far ...
> To: Jim Thomson <Jim.thom@telus.net>, amps@contesting.com
>>
> Hi Jim,
> To my knowledge, rods are not made (as standard parts) in 43... a few
> cable cores could be stacked.
## Type 43 rods are readily available from SSON. [ 1/2" diam x 8"
long. ] I use em all the time for bifilars.
I also discovered something a while back. The large Type 43 /77
beads... [ 1" OD x 1/2" ID x 1" long] will slide over the 1/2" rods
like a glove ! I slid 8 x type 43 beads over the 8" long rod.
I ended up with a solid mass of type 43.... 1" solid x 8" long. The
weight is now quadruple. [ double the diam of anything, and cross
sectional surface area = 4 x as much. Turns out those beads are a hair
bigger than .5" ID. So for those of you who have an application for a 1"
od rod, that's a cheap and dirty way to achieve it.
>
> Rod cores don't have anywhere near the effective mu of a toroid. Because
> of the open magnetic structure they're less susceptible to DC saturation.
> I haven't looked at the DC flux in a rod core since they can't match the
> performance of the toroid in my original post.
>
> Looking at the Harris RF-110A, for instance, which uses a 115uH choke...
>
> Figuring the free air value of the coil dimensions results in a value
> around 20uH therefore, the core has an effective mu of around 6.
>
> This is a relatively low stress application for the choke as the plate
> load impedance is only in the vicinity of 1000 ohms. Significant RF
> current will flow in this part down on 160.
### partially agreed. When Doug de Maw did his qst article on that
gapped choke u see in the old handbooks, he used a HP vector Z meter...
and stated the Z was " > 100 K ohms, on ALL bands".
Now the XL, of course, increases, as freq increases. Here's the big
question. Do we calculate RF current flowing through the choke on band
XXX, based on XL.... OR Z ????????
Put another way, a B+W 800 choke has aprx 12.1k of XL on 21.45 mhz.
However, it's series resonant.. and Z is through the floor.
## With lower values of uh, [esp low bands] the C1 tune cap has to be
increased somewhat. The lower XL ....."eats pf" from the tune cap.
I found with the test set up, [ mfj on output of PI net,
and resistor = plate load Z between anode and chassis] that with a typ
180 uh plate choke, C1 had to be increased by 40 pf on 160m. With
choke removed, C1 value dropped by 40 pf.
## On my hb gg amps.... we used 2 x chokes , at right angles. Big one is
135-180 uh, small one is 45-70 uh. 3 x 500 pf doorknobs in parallel,
wired between junction of chokes and input of a SPST
vac relay. Output of vac relay goes to chassis. Also, 3-5 x 1 meg, 3
watt mof resistors in series, are wired between junction point of chokes...
and chassis. 3 x 4700 pf disc ceramics used for bypass
at base of big choke. [ ceramite brand, 10/15 kv, available from both Henry
radio + mouser].
## Both chokes used on 160m only. Small choke used on 80-10m.
IF both chokes used on 80m, then all hell breaks loose. vac relay just
grnds the cold ends of the 3 x 500 pf caps. [80-10m]
The resistor's just ensure the 3 x 500 pf caps are chassis grnded, for DC.
This set up works very well. Both chokes wound with 22 ga wire.
## Now here's the kicker. One night, my buddy had the big choke removed,
and on the bench. The amp ran flawlessly on 160M... with just the 45 uh
small choke in the circuit. The only difference was,
the C1 tune cap had to be increased a whole bunch. No big deal, since
the vac Tune cap had plenty of excess pf. The 3 x 500 pf doorknobs
didn't cook, or any thing else amiss.
This is on a large metal GG triode, [1350 ohm plate load Z] . So what
gives here ? One 'theory' is the Tune cap + 45 uh choke form a
parallel resonant circuit, making
the choke look like a high Z circuit. We have been trying ridiculous
amounts of low uh/ XL plate chokes on the low bands [ C1 had to be
increased of course].. and in no case, did the bypass caps at the
base of the plate choke ever cook. [ 4700 pf 6-15 kv discs]
## After all this... I'm not about to go on a quest to use a 1- 2.5 Mh
plate choke for the low bands. Simpler to use a 180-250 uh choke, and
simply increase C1 by 40 pf.
Besides, the various metal GG triode's have between 33-52 pf of stray C,
between anode and grid, which is directly in parallel with the Tune cap.
later......... Jim VE7RF
>
> The task would be more difficult using a 4-1000A with 5KV on the plate &
> 5K ohms plate impedance! :-)
>
> 73 & Good morning,
> Marv WC6W
>
> http://wc6w.50webs.com/
>
>>
>> ##? OK... why wouldn't just plane? 16-24 ga?
>> magnet wire,? wound like a solenoid, on say type 43 rod
>> work ????[ like polyimide /kapton magnet
>> wire..? with the 10-15 kv insulation]? ? Why
>> would .5 to 2 amps of dc plate current? saturate the
>> type 43 material ??
>> It's a RF plate choke.. so should present a high Z.
>>
>> ##? I have see pix of the harris? plate chokes...
>> and they used a HUGE? chunk of ferrite inside a form..
>> with the usual magnet wire [ with way less turns than a typ
>> ham choke]? wound on top of the same form.? It
>> worked down to 1.6 mhz.. and no series resonances from?
>> 1.6 to? 32 mhz.?
>>
>> Jim? VE7RF
>>
>>
>>
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 15 Jan 2010 12:35:39 -0600
> From: Rob Atkinson <ranchorobbo@gmail.com>
> Subject: Re: [Amps] which HV connector to use?
> To: Alex Eban <alexeban@gmail.com>
> Cc: amps@contesting.com
> Message-ID:
> <d2bb1cb81001151035ifde61anb30c9f4706cc07fd@mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> okay guys thanks vy much. I'm getting a better picture now on how to
> proceed.
>
> 73
>
> Rob
> K5UJ
>
> On Fri, Jan 15, 2010 at 9:46 AM, Alex Eban <alexeban@gmail.com> wrote:
>> Guys, we played around with this a while ago!
>> Use ignition wire - copper, NOT carbon core- and wire it point to point
>> if
>> you're afraid of connectors. It's rated to about 20 kV and easily handles
>> 1
>> or 2 Amps.
>> Alex ? ?4Z5KS
>>
>> -----Original Message-----
>> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>> Behalf Of Rob Atkinson
>> Sent: Thursday, January 14, 2010 11:32 PM
>> To: amps@contesting.com
>> Subject: Re: [Amps] which HV connector to use?
>>
>> I'm trying to get my head wrapped around all this.
>>
>> I am planning a h.v. supply homebrew project and have most of the parts
>> (but
>> every time I think that something like this comes up).
>>
>> I want to build a separate B+ supply for my Ten Tec Centurion amp.
>> The idea is to have a supply that does not increase the voltage but
>> increases the current capability and goes from ICAS to CCS. ?It's partly
>> unnecessary I admit, but it started with good intention and also as a
>> learning exercise (which it still is). ?The idea is to make the Centurion
>> capable of handing high duty cycle modes and AM, but the power supply
>> will
>> also be useful for other future projects, supplying
>> 3.2 KV at 1.5 A CCS.
>>
>> I bought some h.v. wire and those millen plug/jack pairs from RF Parts
>> a few months ago. ?Now it seems they're inadvisable. ? I admit the
>> h.v. wire seems hard to work with, brittle and hard to strip. ? RG213
>> by comparison is a lot easier to work with. ? I'm getting the
>> impression I should go with that, hardwired into the amp cabinet with
>> SHV connectors on the power supply cabinet. ? Or is this overkill for
>> 3.2 KV?
>>
>> 73
>>
>> Rob
>> K5UJ
>> _______________________________________________
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>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>
>
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> End of Amps Digest, Vol 85, Issue 29
> ************************************
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