[HBQRP] VFO Toroid saga

Thu Nov 24 22:33:21 EST 2005

Steve...

I found one thing I like about your original wooden PC board holders...  I
can power the circuit while it is the holder without having to worry about
shorting anything. :)

I hope everyone had a HAPPY THANKSGIVING...

I'm trying to work off the turkey with a soldering iron... I don't think
it's gonna work... having too much trouble bending over the workbench to see
what I'm doing :)

Darrel... K0AWB

-----Original Message-----
From: hbqrp-bounces at mailman.qth.net
[mailto:hbqrp-bounces at mailman.qth.net]On Behalf Of Darrel Swenson
Sent: Wednesday, November 23, 2005 5:54 PM
To: Midwest Homebrewers Group
Subject: RE: [HBQRP] VFO Toroid saga

Steve...

I got a chance to play with some toroids this afternoon...

I wound 29 turns of 22 gauge, 26 gauge, and 30 gauge on 3 T50-6 cores.  I
also tested the original with 29 turns of 24 gauge.

29 turns, 22 gauge, T50-6 = 2.435 MHz
29 turns, 24 gauge, T50-6 = 2.456 MHz
29 turns, 26 gauge, T50-6 = 2.475 MHz (2.40 - 2.48 MHz)
29 turns, 30 gauge, T50-6 = 2.350 MHz (2.28 - 2.41 MHz)

28 turns is really about all the 22 gauge wire that will fit on a T50 core.
I got 29 on, but a couple of the windings don't lay completely flat.  The 24
and 26 gauge fit fine.

The 30 gauge is pretty loose.  I was able to play with it a little... by
pressing the winding closer together the oscillator frequency went down.
Spreading them out equally caused the frequency to go up.  I could move the
frequency from 2.28 to 2.41 by compressing and expanding the windings.

I got the same results with the 26 gauge wire, but not as much swing.

The 24 and 22 gauge wire are too tight to move much.

I'm guessing this is why designers use the largest wire gauge that will fit
on the core... better stability.

I couldn't find any reference to 2.4 MHz VFO frequency either.  It does say
the IF is 7.68 MHz...

So... 10.1 MHz operating frequency - 7.68 MHz IF leaves 2.42 MHz for the
VFO.

We still have to add C7 and the tuning diode so the final frequency range
will changed slightly.

Darrel...

-----Original Message-----
From: hbqrp-bounces at mailman.qth.net
[mailto:hbqrp-bounces at mailman.qth.net]On Behalf Of ssellmeyer
Sent: Wednesday, November 23, 2005 4:41 PM
To: K0AWB at Cox.net; Midwest Homebrewers Group
Subject: Re: [HBQRP] VFO Toroid saga

Ohhhhhhhhhh Noooooooooo ! !  I just rewound it for 40 M  with the present 23
turns............and I have a 30M kit. Duhhhhhhhhhhhhh. I forgot the Elmer
101 is for a 40M version. Duuuuuuuuhhhhhh #2

I looked thru the instructions that came with the kit but didn't see where
the 2.4 Mhz was referenced anywhere.
Oh well. Back to the drawing board !

SteveWBØQQT      P.S. Yes Dar, we are Grrrrrrrrrrr..........having fun
now.........I think !

----- Original Message -----
From: "K0AWB at Cox.net" <k0awb at cox.net>
To: "ssellmeyer" <ssellmeyer at inebraska.com>; "Midwest Homebrewers Group"
<hbqrp at mailman.qth.net>
Sent: Wednesday, November 23, 2005 2:50 PM
Subject: RE: [HBQRP] VFO Toroid saga

> Steve and everyone...
>
> Sounds like you are having fun experimenting.  Keep winding those toroids.
>
> As I was winding toroids this afternoon... I was trying to figure out why
> Steve was getting such different results than I did... then it occurred to
> me...  he isn't... :)
>
> The VFO in the 40 meter version runs at 3.000 - 3.035 MHz with a 4.00 MHz
IF
> to cover  7.000 -  7.035 MHz (40 meters)
>
> The VFO in the 30 meter version runs at 2.420 - 2.455 MHz with a 7.68 MHz
IF
> to cover 10.100 - 10.135 MHz (30 meters)
>
> The VFO in the 20 meter version runs at 5.000 - 5.035 MHz with a 9.00 MHz
IF
> to cover 14.000 - 14.035 MHz (20 meters)
>
> I thought the 25 turns on L1 sounded familiar... that's the number I just
> wound on L1 for the 40 meter version I'm building.
>
> The 40 meter version uses 25 turns for a 3.0 MHz VFO.
>
> The 30 meter version has 4 more turns to drop the VFO frequency down to
> 2.4..something MHz.
> So if 23 turns = 3.071 MHz.
>       25 turns = 2.890 MHz
>       27 turns = 2.625 MHz
>       29 turns should be about 2.4 MHz... for 30 meters.
>
> Don't worry about getting the VFO exactly on frequency, we calibrate it in
a
> later step.
>
> 73... Darrel... K0AWB
>
> -----Original Message-----
> From: hbqrp-bounces at mailman.qth.net
> [mailto:hbqrp-bounces at mailman.qth.net]On Behalf Of ssellmeyer
> Sent: Wednesday, November 23, 2005 12:03 PM
> To: Midwest Homebrewers Group
> Subject: [HBQRP] VFO Toroid saga
>
>
> Short and sweet, here are this mornings experiments. As stated earlier I
had
> 27 turns of # 22 wire on the toroid which gave me 2.625 Mhz.
>
> After removing 2 turns (now at 25 turns) I had 2.89 Mhz. Looks like I'm
> getting there eh ??
>
> Removing two more turns (now at 23turns) I have 3.071 Mhz. Think I'm going
> to leave it there and see what happens later.......if anything.
>
> I was Talking to KØNG, Charlie, last night here in Lincoln on 2 meters and
> told him the situation. He is an RF design engineer for Telex here in
> Lincoln and has bailed me out on occasions too numerous to mention here.
He
> explained it to me as the same as trimming a dipole for the resonant
> frequency you are trying to achieve. In other words you remove turns to
> raise the frequency or add turns to increase. Made sense to me !  It
appears
> to have worked. How about that. This old dog learned something ! !
>
> Dale, in regards to the Radio Shack freq. counter and using a probe, I
tried
> your method of NOT physically touching the board at Q2. I played around
with
> resistor leads, a sewing needle and insulated wire but could not get a
> reading unless I touched it physically. I used the sewing needle to touch
it
> with since my RF probe also uses a needle. I agree with you on the
> possibilites of loading, interaction etc. Many thanks for the tip. I'm
here
> to learn and you guys are a big help.
>
> Lunchtime.............Steve/WBØQQT
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>

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