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

[rocketnj at gmail.com]

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%
>