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PostPosted: Dec Sat 02, 2006 3:20 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3077
Location: aston, pa, usa
Whose part number is F-82-61 for the toroid and does Mouser have an equivilent? by sparky
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CWS/Bytemark and I didn't find it on Mouser, maybe Mouser does have it and I just can't work the website right.
http://www.cwsbytemark.com/prices/toroidal.php


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 Post subject:
PostPosted: Dec Sat 02, 2006 3:30 am 
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Location: aston, pa, usa
I thought Curt answered that question. It's the tuning coil parallel to the var cap in his schematic. It is an F-82-61 toroid from CWS http://www.cwsbytemark.com/prices/toroidal.php with about 35 turns. Like Norm said, you can use a solenoid coil or an AA5 antenna.
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-Mike Tôôn
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I brought this over from another thread called "tuning the 6888" on homebrew.


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 Post subject:
PostPosted: Dec Sat 02, 2006 5:09 am 
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Posts: 459
Location: Collison, IL USA
bill hamre wrote:
I thought Curt answered that question. It's the tuning coil parallel to the var cap in his schematic. It is an F-82-61 toroid from CWS http://www.cwsbytemark.com/prices/toroidal.php with about 35 turns. Like Norm said, you can use a solenoid coil or an AA5 antenna.
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-Mike Tôôn
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I brought this over from another thread called "tuning the 6888" on homebrew.


You could probably get away with a 230-270 uH choke, even the little 30 cent epoxy ones are good for 50-75 mA, the plate won't be drawing more than that. That and a little trimmer for the 250 uf cap would save lots of acreage.


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 Post subject:
PostPosted: Dec Sat 02, 2006 12:22 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: aston, pa, usa
You could probably get away with a 230-270 uH choke, even the little 30 cent epoxy ones are good for 50-75 mA, the plate won't be drawing more than that. That and a little trimmer for the 250 uf cap would save lots of acreage. by Neutrodyne
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Where were you, masked man, when I was ordering these parts? If we get more than 10 requests I'll spec this in for the next 10 unless someone disagrees. Also, Neut, post a link for me to order from.


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 Post subject:
PostPosted: Dec Sat 02, 2006 12:53 pm 
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Location: Vieques, PR, USA
I wouldn't use the little chokes. Abysmal Q compared to the toroid for a tuned circuit.
CWSByteMark is generally pretty fast and easy to deal with. Ocean State would also have the Amidon ones FT-82-61. Mouser doesn't seem to have any RF toroids.

-Bill


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 Post subject:
PostPosted: Dec Sat 02, 2006 5:30 pm 
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Posts: 747
Location: Westminster, MD
Neut,

If you are talking about the tuner across the coil I assume you mean 250pf not uf. Do you have a source for a trimmer that large? The largest one I can find only goes to 70pf.


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 Post subject:
PostPosted: Dec Sat 02, 2006 5:38 pm 
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Sparky74 wrote:
Neut,

If you are talking about the tuner across the coil I assume you mean 250pf not uf. Do you have a source for a trimmer that large? The largest one I can find only goes to 70pf.
You can use the small (oscillator) section of a var cap from a AA5. No big deal here.


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 Post subject:
PostPosted: Dec Sat 02, 2006 5:57 pm 
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Sparky74 wrote:
Neut,

If you are talking about the tuner across the coil I assume you mean 250pf not uf. Do you have a source for a trimmer that large? The largest one I can find only goes to 70pf.


Aside for the oscillator padder from an aa5 you could parallel a 200-250 fixed with your 70pf trimmer to get in the ball park.

I was going to wind a seloniod on piece of ABS. I can easily make a space wound with my lathe. Is there any advantage to doing that in this application? How about making an "air dux" type self supporting coil? That is easy too. CD case plastic makes nice ribs. In many "real" transmitters one uses the air dux and a link coil feeding a dipole. Would that be to effecient and possibly give to much output? I do not have the proper torrids, and seloniods have a higher Q anyway, that is why I was thinking of a seliniod.

I have some HC-6? crystals in the BCB. The crystals I am talking about are about 3/4" by 5/8". Will they oscilate in this circut? How about using harmonics of a crystal like, a 1.4 mhz tuned to 0.7 mhz?

Comments.....


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 Post subject:
PostPosted: Dec Sat 02, 2006 8:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3077
Location: aston, pa, usa
To keep it simple mail me a $5.00 check with your address on it to 2950 concord rd #16,aston,pa,19014. The parts are qty 1 each of:

0-TCF100-x 1,000 KHz Mouser
F-82-61 Torrid
5.1 volt zener diode


Last edited by bill hamre on May Fri 10, 2013 6:30 pm, edited 1 time in total.

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 Post subject:
PostPosted: Dec Sat 02, 2006 8:44 pm 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34326
Location: Sandpoint, IDAHO 83864
I also prefer solenoid type coils. They have a higher Q and are more efficient than toroids. I leave the toroids to the solid state builders. But to me in a tube transmitter, they just "don't fit".

As for doubling the frequency, it can be done, and is done in a lot of transmitters. But you are walking on thin ice here. I would not suggest anybody trying it unless they have a decent understanding of how transmitters work and the things that can happen if you do it without experience tuning the output.

Since you would be going for emphasized second harmonic content from a 700kc crystal to deliver output on 1400kc, what you are going to do is to bolster the harmonic output. But what happens to the third and fourth and so on harmonics? I know there isn't much on 2100kc or 2800kc, but the fifth harmonic on 3500kc could get you into trouble with hams in the neighborhood. \

Our local AM station, KSPT, is on 1400 and I live about three miles as the crow flies from that Gates BC-1T and its vertical antenna. When I lived about two miles from it, I could and did use the 5th harmonic to set my bandspread dial on 7000kc to spot the low end of the 40 meter ham band.

Good transmitter design practice calls for some rather complicated for the beginner tuning networks in the output circuit to keep the harmonics filtered out when the final amplifier is also frequency multiplying. To add those tuned circuits would take the simple transmitter out of the realm of something simple for most people. Besides, I don't see anything wrong with 700kc, unless you have a local BC station on that spot.

And please don't get the idea that low efficiency coils or other components will keep your output down. Yes, it will, but it goes against the grain of us old time transmitter builders where maximum efficiency was, and is, always the goal! Just the thought of doing something like that on purpose to keep down the output is a very sickening thought to me! If you want to cut down the output, reduce your voltage or waste your output in a dummy load, but PLEASE do not design in known inefficiency in the circuit.
Curt

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(Connoisseur of the cold 807) CW forever!


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 Post subject:
PostPosted: Dec Sat 02, 2006 9:24 pm 
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Posts: 11100
Location: Vieques, PR, USA
Curt Reed wrote:
I also prefer solenoid type coils. They have a higher Q and are more efficient than toroids. I leave the toroids to the solid state builders. But to me in a tube transmitter, they just "don't fit".


An FT-**-61 will have considerably better Q compared to say a little BCB coil wound on a 1" form. To the tune of double or triple the Q. To get in the range where they are comparable you'd need a 3-4" solenoid coil. Self-shielding too!

Well, beyond a point in this particular project its not going to make any difference. You can always hide the toroid inside an authentic looking coil. :)


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 Post subject:
PostPosted: Dec Sat 02, 2006 9:47 pm 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34326
Location: Sandpoint, IDAHO 83864
When I mentioned using a solenoid coil form, I was assuming that the coil winder knew about diameter versus length and such. Sorry if I said something that may confuse the newer guys. Just another old fart speaking from many years of experience. Bill is correct, for small coils, the toroid may be better.
Curt

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Curt, N7AH
(Connoisseur of the cold 807) CW forever!


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 Post subject:
PostPosted: Dec Sat 02, 2006 10:22 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 795
Location: Gulf Breeze, FL USA
Uh-Oh, I may be in a little trouble here :? . In Norm's instruction sheet it says "Use any broadcast band antenna coil". So, since I sacrificed a radio to build this project, I am planning on using the antenna coil that was in the radio. Maybe I took the instructions a little too literally?
Ben


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 Post subject:
PostPosted: Dec Sat 02, 2006 10:55 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1086
Location: Zip : 80751
I used a ferite rod antenna from a 50's or 60's small plastic radio that cost me a dollar at a garge sale. It works fine. i also guessedtimated a 100 pF cap would be about right, for the cap across it. I'm sure its a little off, but i had a very limited amount of space to build in. used a little enclosure form radio shack along with a 1.2 amp transformer full wave rectified, and a small output transformer from an old junker radio. using about 3 foot of antenna and i get about 100~150 feet of coverage in all directions.


Jeremy


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 Post subject:
PostPosted: Dec Sat 02, 2006 11:09 pm 
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Posts: 747
Location: Westminster, MD
Curt,

By the way, what do you mean by "cold" 807? My first (CW) transmitter made from the Radio Amatuers Handbook called for an 807 but not having one I was forced to beg a 6146 that we used in the mobile units final, the substitute worked pretty good.


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 Post subject:
PostPosted: Dec Sat 02, 2006 11:22 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 795
Location: Gulf Breeze, FL USA
Hi Jeremy,
Thanks for the input. So, if I understand correctly, you have the ferrite loop and a 100pf cap between the 6888 plate and B+, instead of the torroid and variable cap seen in the earlier posts?
If so, that's great for me since this radio has a loopstick that attaches to the variable cap.
Ben


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 Post subject:
PostPosted: Dec Sun 03, 2006 12:25 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34326
Location: Sandpoint, IDAHO 83864
Sparky- The cold 807 is an old ham saying about cold beer. Where or when the saying originated is beyond me, but I recall hams using the term at least 40 years ago. I guess newer hams could use the term cold 6146, but it just does not ring a bell like a cold 807 does. Today to be politically correct, we would probably call it a cold "adult beverage", but I don't go for that politically correct bull s**t! I was raised in the old days when we said what we wanted to say without any fear of upsetting the modern PC crowd.
Curt

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(Connoisseur of the cold 807) CW forever!


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 Post subject:
PostPosted: Dec Sun 03, 2006 2:33 am 
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Joined: Sep Tue 12, 2006 2:01 pm
Posts: 91
Location: Goshen (near Cincinnati,Oh)
I got my tube today. Thanks Norm! Now I am on my quest for parts. I found a 6.3v transformer in my parts box and I think I can find most everything else.

I am planning on taking the antenna coil and tunner out of a junk transistor clock radio. Octal tube socket I will probably order from Ebay.

I have some wrinkle paint. I might try to make the chassis look somewhat like a Crosley Pup. So that would require me to keep the parts small.

The thing I am having trouble finding is the 120v transformer. What I would really like is one small transformer with taps for 6.3v and 120v. Does anyone know where to order such a thing? The 6.3v transformer I have is small so a small 120v transforme might work also. I had thought about going with a transformerless design. But have almost rejected that for safety reasons.

_________________
Adam
KA9CBT


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 Post subject:
PostPosted: Dec Sun 03, 2006 2:45 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 795
Location: Gulf Breeze, FL USA
Laseradam,
I ordered one from oldradioparts.com. There is a $20.00 minimum order, but I'm like a kid in a candy store when surfing that site, and never have any trouble finding enough stuff to meet the minimum. You'll find the tube socket there too.
Ben


Last edited by Cathode Follower on Dec Sun 03, 2006 4:20 pm, edited 1 time in total.

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 Post subject:
PostPosted: Dec Sun 03, 2006 2:16 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3077
Location: aston, pa, usa
used a ferite rod antenna from a 50's or 60's small plastic radio that cost me a dollar at a garge sale. It works fine by Jeremy
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I bought one for 25 cents at Kutztown which I'll send free to anyone who wants to try Jeremy's design.


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