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 vswr indicator and variable resistor 
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Post vswr indicator and variable resistor
i use the below circuit quite a bit , i have made onother circuit built on a DPDT switch but i haven't got any 10k variable resistors for RV1 , can i use a fixed instead ?, to be honest in the past i havn't had to adjust them so not sure if they do too much, i think it's just for calibrating the meter but i only use an LED .

Is this the max resistance it offers ? and it can be varied down ?

was thinking of playing safe and stick a 5k fixed on or should i leave off?


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Voice is for CBers, amateur radio operators, the average citizen, and the military. In other words, voice is for everyone with a mouth. CW is for those who choose this newer mode of communication. Newer? Why yes. Voice has been around for a million years.
Sun Feb 26, 2012 4:30 pm
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 vswr indicator and variable resistor 
Silent Key

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Post Re: vswr indicator and variable resistor
Billy,

RV1 can be a fixed value - just select it to give the required result on whatever your display is.

73,
Steve G3TXQ


Sun Feb 26, 2012 5:36 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
cheers steve


billy

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Sun Feb 26, 2012 5:38 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
Billy, do you have any links to sites for QRP ATU's, as i want to build
a ATU and VSWR bridge to go with my K2.

Phil


Sun Feb 26, 2012 6:10 pm
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 vswr indicator and variable resistor 
Silent Key

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Post Re: vswr indicator and variable resistor
Here's one possibility; it's "one I made earlier"! It's the unit to the left of the all-band QRP CW/SSB radio:

Image

Schematic is here - ignore the TIC keyer components:
http://www.karinya.net/g3txq/cubii/atu.jpg
It's easy to scale the SWR indicator up to higher power if you need it.

Just realised the inductor toroid is specified wrongly - it should be a T106-6 :)

73,
Steve G3TXQ


Sun Feb 26, 2012 6:40 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
G7BZD wrote:
Billy, do you have any links to sites for QRP ATU's, as i want to build
a ATU and VSWR bridge to go with my K2.

Phil


To be honest Phil , i suppose it depends what sort of antennas you will be using /power etc , i can get away with a lot because im on flea power most of the time .. The vswr indicator for example i was able to just use 2x 100R 0.5 w resistors to give me 50 ohm 1 watters as the rig will be around 500mw Caps i can get away with polvaricons etc...

I think the standard K2 does about 15 watts doesn't it ? if so i would be tempted to make one for at least that just so you CAN up the power if you want.. that may be out the designs of lots of qrp atu designs..

To be honest my personal opinion is end fed are the easiest and quickest to deploy /p that's why i have gone with the L network mini tuners i'm messing with .. I'm on a mission for this summer to go ultra light :)

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Sun Feb 26, 2012 6:54 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
Steve.

Think i get 15w out before it starts to smoke.

Billy.

Yes it does 15w max. Am looking at end feds. Have a 10mtr windsock pole and theres a nice
summer spot up the road called Tennyson Down, thats my summer aim, light weight and portable.

Thanks

Phil


Sun Feb 26, 2012 6:56 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
G3TXQ wrote:
Here's one possibility; it's "one I made earlier"! It's the unit to the left of the all-band QRP CW/SSB radio:

Image

Schematic is here - ignore the TIC keyer components:
http://www.karinya.net/g3txq/cubii/atu.jpg
It's easy to scale the SWR indicator up to higher power if you need it.

Just realised the inductor toroid is specified wrongly - it should be a T106-6 :)

73,
Steve G3TXQ


looks a nice doable design that steve

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Sun Feb 26, 2012 6:57 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
G7BZD wrote:
Steve.

Think i get 15w out before it starts to smoke.

Billy.

Yes it does 15w max. Am looking at end feds. Have a 10mtr windsock pole and theres a nice
summer spot up the road called Tennyson Down, thats my summer aim, light weight and portable.

Thanks

Phil


http://www.youtube.com/watch?v=_93BsL2W ... plpp_video

check the vid out , schematic right at end ... i made one but used cores for the inductors , you should get 15 watts through a polvaricon but steve will know better.. mines just a bit bigger than a box of matches :)

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Sun Feb 26, 2012 7:00 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
heck that is small. would have trouble finding it in my shack.

Phil


Sun Feb 26, 2012 7:11 pm
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 vswr indicator and variable resistor 
Silent Key

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Post Re: vswr indicator and variable resistor
You can't put a sensible power rating on a tuner without knowing what the antenna load impedance will be; the failure mechanism will then either be heat dissipated in the inductor, or voltage breakdown of the capacitor.

I've never seen a voltage spec for the polyvaricon capacitors; I'm sure they would be OK at Billy's power levels, but I could believe they might fail at 15W with an adverse load impedance. And don't forget that capacitor breakdown is instantaneous - just one voice peak is enough to do it - whereas inductor over-heating will be related to average power levels.

Steve G3TXQ


Sun Feb 26, 2012 7:17 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
anything higher than 5 watts i would be tempted with an air spaced variable anyway for what they cost for low power application .. I'm just going through this small as possible phase at the moment .. Once it's out my system i want to try qro so will need caps that will handle 5 watts anyway :)

Re the K2 , i would be tempted to go with the internal tuner option , one less thing to set up and carry.. That said the one in my K1 isn't great ..

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Sun Feb 26, 2012 8:26 pm
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 vswr indicator and variable resistor 
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Post Re: vswr indicator and variable resistor
I am also thinking that the internal one will be the way to go.

Just got to order the kit and get it built, unless i can find one that someone has spare
after upgrading from a K2/10 to a K2/100.

Phil


Sun Feb 26, 2012 8:39 pm
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