[Elecraft] K1-4 low power and poor receive on 40 meters

[Dave]

Thanks Don

I am borrowing a military surplus RF voltmeter with probe this afternoon. I was thinking the crystal also.  Not many parts in the circuit.

Thanks for the pointers.

73
Dave wo2x

Sent from my iPad

> On May 20, 2020, at 2:36 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
> 
> There is the possibility that the 40 meter crystal has low activity.
> Check the RF voltage at pin 4 of P1 on the band board.  You should read 70mV or more with an RF Probe or 200mV+ peak to peak if using a 'scope with a 10X probe.
> 
> A good working K1 will develop at least 5 watts.
> Make up an RF probe if you don't have one.  It does not have to be fancy, just stick the component leads through a piece of cardboard and solder the leads together.  You need a 1N34 diode (not a silicon diode) Elecraft does have a kit.
> 
> 73,
> Don W3FPR
> 
>> On 5/20/2020 1:35 PM, rocketnj at gmail.com wrote:
>> Hi Don
>> 
>> I have done that using the Marconi for RX, then touching up for TX. I understand 40 is a combo of 30 & 40 settings. After carefully retuning (done it several times) the best I can get on 40 is about 60 to 75 mW. 30 makes better than 2 watts. The menu for power out is set to 2.0 on 40. Receive sensitivity is 10 to 15 dB down from 30 meter receive.
>> 
>> I read that the windings on T3 and T4 are critical. I have counted the turns and verified which side #1,2,3 and 4 are coming off the core. Both T3 and T4 appear to be fine. There is enough wire left over in the box the radio was in so I can rewind T3 or T4. From what I see on the schematic T4 would most likely be the suspect (if it is the transformer.)
>> 
>> I am going to borrow an RF Power meter with probe and check 30 vs 40 meter readings on the Premix in & out and the RF filter in & out. That will greatly help pinpoint the issue.
>> 
>> 73
>> Dave wo2x
>> 
>> 
>> -----Original Message-----
>> From: Don Wilhelm <donwilh at embarqmail.com>
>> Sent: Wednesday, May 20, 2020 11:39 AM
>> To: rocketnj at gmail.com; elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] K1-4 low power and poor receive on 40 meters
>> 
>> Dave,
>> 
>> Refer to the K1FL4 instructions and re-tune the trimmers on the filter board.  They MUST be done in the proper band sequence - 30 meters before 40m, 15m before 20m.  The PreMixer portion is usually the most critical for power output.
>> 
>> 73,
>> Don W3FPR
>> 
>>> On 5/20/2020 11:20 AM, rocketnj at gmail.com wrote:
>>> Hi All,
>>> 
>>>   
>>> I am going to sell a K1-4 (4 band 40, 30, 20, 15) for the estate of my
>>> Elmer. In testing the radio I found 40 meters is about 15dB less
>>> sensitivity than 30 and power out about 75 mW. I have double checked
>>> the values of components on the filter board to ensure they are
>>> correct and installed correctly. I also checked T3 and T4 which can
>>> cause issues on 40. T3 has 23 turns on the secondary with three turns
>>> on the primary. T4 has 24 turns on secondary and two turns on primary.
>>> Another symptom is the CH trimmer cap seems to be at one end of tuning range (not seeing double peak).
>>> 
>>>   
>>> Note - the radio does not have the ATU option and 30 meters is set for
>>> 10.1 MHz and not 10.0 (double checked crystals).
>>> 
>>>   
>>> >From what I can measure so far the relays seem to be working "as designed".
>>> When I switch from 15 meters to 40 meters I can see the pulses to the
>>> relays to switch them (latching relays. I did notice in the 4 band
>>> filter manual it says K6 relay is not active on 40 but I do see it
>>> active and looking at the schematic K6 switches between 15/20
>>> operation and 30/40 so I think there is a typo in the filter board manual at the bottom of page 23.
>>> 
>>>   
>>> I am using a Marconi service monitor for testing. I have not built an
>>> RF probe yet and hoping someone has seen this symptom before. I would
>>> like to get the K1 fully operational as the proceeds are going to my
>>> Elmer's widow 100%
>>> 
>