T1 build...

[Ross Primrose N4RP]

Got my T1 kit last night, got the parts inventoried, and got up to where
I need to start winding the toroids... I did notice one thing on the
schematic that left me puzzled though, there doesn't seem to be any DC
return path for the relay coils. Am I missing something?

73, Ross N4RP

--
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”

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[Don Wilhelm-4]

  Ross,

You are looking too hard!  Most of the Elecraft tuners use the same
technique - the selected relay is activated and the return path flows
through all the rest of the other relay coils - there is not enough
current through any one coil to activate them, and it works quite well -
one more piece of "magic" that can be done using PICs.

73,
Don W3FPR

On 3/4/2011 1:30 PM, Ross Primrose N4RP wrote:
> Got my T1 kit last night, got the parts inventoried, and got up to where
> I need to start winding the toroids... I did notice one thing on the
> schematic that left me puzzled though, there doesn't seem to be any DC
> return path for the relay coils. Am I missing something?
>
> 73, Ross N4RP
>
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[Ross Primrose N4RP]

OK, so I finished the build yesterday, and today, after I built another
BNC-PL259 cable so I could hook it up, I did the performance tests.  
Everything seems OK, except the transmit power display tests.  The T1
shows the correct power level, but the K3 indicates at >10:1 SWR during
the power measurement.  Bypass mode works fine, if I put the T1 in
bypass and hit the tune switch on the K3 the dummy load gives a 1:1 SWR,
it's only a problem when trying to display power....

Ideas?

73, Ross N4RP

On 3/4/11 2:26 PM, Don Wilhelm wrote:

>  Ross,
>
> You are looking too hard!  Most of the Elecraft tuners use the same
> technique - the selected relay is activated and the return path flows
> through all the rest of the other relay coils - there is not enough
> current through any one coil to activate them, and it works quite well
> - one more piece of "magic" that can be done using PICs.
>
> 73,
> Don W3FPR
>
> On 3/4/2011 1:30 PM, Ross Primrose N4RP wrote:
>> Got my T1 kit last night, got the parts inventoried, and got up to where
>> I need to start winding the toroids... I did notice one thing on the
>> schematic that left me puzzled though, there doesn't seem to be any DC
>> return path for the relay coils. Am I missing something?
>>
>> 73, Ross N4RP
>>

--
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”

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[Don Wilhelm-4]

  Ross,

Who knows what the L and C values are that are in your T1 until you do a
TUNE.  The incication of a low SWR when the T1 is in bypass indicates
that there is residual reactance when in non-bypass.  Doing a TUNE
should straighten things out.  The settings are remembered by band, so
do a TUNE on each band.

73,
Don W3FPR

On 3/6/2011 8:22 PM, Ross Primrose N4RP wrote:

> OK, so I finished the build yesterday, and today, after I built another
> BNC-PL259 cable so I could hook it up, I did the performance tests.
> Everything seems OK, except the transmit power display tests.  The T1
> shows the correct power level, but the K3 indicates at>10:1 SWR during
> the power measurement.  Bypass mode works fine, if I put the T1 in
> bypass and hit the tune switch on the K3 the dummy load gives a 1:1 SWR,
> it's only a problem when trying to display power....
>
> Ideas?
>

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