[Elecraft] 160 meter low transmit

[W3FPR - Don Wilhelm]

Don,

With that information, I would suspect the bandpass filter (even if it
receives 160 meters fine) - re-check C13 and C14 for the correct value of
1200 pf.

If that does not correct things, use an RF probe or 'scope and compare RF
Voltages between 160 meters and 80 meters with the power set at about 5
watts.  Check at the following points (you can stop at the first one that is
substantially lower on 160) - cathode of D6 or D7 first - then at jumper
W6 - then the collector (case) of Q5 - next the collector (tab) of Q6 - then
the collector of Q7 and collector of Q8.

Let us know where the 160 meter RF is being lost (RF Voltage substantiallly
less than that on 80 meters) and we can likely home in on the problem area.

73,
Don W3FPR

> -----Original Message-----
>
> My K2 is serial 1683.  I built it in 2000.  With my initial kit,
> I added the
> SSB capability and the 160 capability; however, since I didn't have a 160
> antenna then, I didn't complete the 160 alignment.  I built the
> KPA100 over
> the weekend and before closing up the rig, I decided to align 160.  When
> applying the 2 watts via the power dial and adjusting L3 and L4, I can get
> no more than 1.3 to 1.4 watts out.  I do receive 160 signals, and well at
> that.  I compared my K2 to my FT-1000D and the K2 signal is received more
> strongly.  I first reheated all the solder points including those
> mods that
> were done to the RF board for the 160 capability and the pin
> connectors, but
> no increase in power.  I demounted the toroids on the module,
> retinned them
> and put them back, but still no increase in power.  I tested the
> toroids for
> continutity on the tinned elements before remounting them, and they tested
> fine.
>
> I measure 1.3 to 3 volts at R30 from 1800 to 2000.  I connected a
> dummy load
> in front of the LPF and get the 1.2 watts there.   Adjusting the
> power knob
> doesn't change the output at all.  I took apart the LPF and
> tested each Cap
> and values are fine.  L5 is the correct value.  I pulled and test
> C75, C13,
> and C14, all ok.  All the Caps in the pre-driver, driver and power amp are
> all the correct values.  The only one I couldn't check is the one between
> the 2 power transistors on the bottom of the board.
>
> The resistance of my relay coils meets the specifications.
>
> I checked the T4 as noted in the notes on 160 issues on the Elecraft
> website, and mine is to spec with the 3 windings for points 3 and
> 4.  My kit
> didn't have the 39 pf cap for one near U5.  It has a 68 pf.
>
> I am outputting the K2 to a dummy load during my transmit tests.  My power
> supply is outputting 13.8 volts.
>
> Don - KA6AKH
>
--
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.344 / Virus Database: 267.10.15/81 - Release Date: 8/24/2005