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Refinement to TK690H VCO Conversion to 6M

 

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A fellow ham brought over a TK690H that was converted to 6M from the RB article. It worked OK on 6M, except that the VCO voltage was fixed and did not change with the frequency change. Normal range is greater than 1.5 V at the highest frequency to less than 8.0V at the lowest frequency. Also the varactor front end tuning did not change with frequency, so there must be a connection between the two. I think the VCO voltage was fixed to around 5.0 V. The brass rods were protruding about 3 mm above the coil forms.
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I just did a couple more TK690H conversions on the older but better radios with all number serials starting below the number 3..........I say better because of narrower receiver modulation bandwidth of around +-7 KHz vs +- 8.5 KHz on the newer radios with "E" bandwidth ceramic filters instead of "F" bandwidth ceramic filters, for a better signal to noise ratio.? Also the older transmitters with the bipolar PA transistors are more efficient on 6M than the mewer radios with MOSFET PA transistors. The older radios should do 105W with 15A draw all across 6M.
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Another ham from the west coast (sorry don't remember the call) on this group site suggested that he just removed the 2 chip caps in parallel with TC301 and TC302, rather than inserting brass rods into the coils. I tried that first, but that was insufficient on receive above 53.5 MHz, so I suggest doing both, but with a shorter (3mm) length of the 1/8" brass rod.? This way both the capacitance and inductance are lowered possibly about the same amount, and the brass rod is confined completely to inside? the coil form and it is also completely sealed to moisture. I used Permaseal Ultra Blue RTV first placed inside the coil from and then the 1/8" rod inserted centered inside and then covered over with the Permaseal. See pictures. The first shows the tube of Permaseal and the 2 chip caps still in place, and the second with them removed on another radio.
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John W1GPO
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John,
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?Nice revision to the conversion.
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Another unrelated TK690 question.
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Does the TK690 also cover 10 and 6 in one radio?
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Over the past 15 years I have read conflicting information on this and I have even seen some indication of a special programming file to enable 10 and 6 meters in one radio but I have never talked to anyone with a TK690 who can confirm if it's true.
 

No.... The front end can't tune that far. The TK6110 can provided you get the right band split.. I can't recall if it's the low version or the high version that can be modified for entire 10 and 6?

Chris WB5ITT?

On Sat, Mar 1, 2025, 1:21 PM MICHAEL MAY via <may2142=[email protected]> wrote:
John,
?
?Nice revision to the conversion.
?
Another unrelated TK690 question.
?
Does the TK690 also cover 10 and 6 in one radio?
?
Over the past 15 years I have read conflicting information on this and I have even seen some indication of a special programming file to enable 10 and 6 meters in one radio but I have never talked to anyone with a TK690 who can confirm if it's true.
 

Chris Boone - how dose the noise blanker in those radios compare to the Motorola Extender (such as Micor or Syntor)?

**
John Mackey, KS?F
CPBE-8VSB-DRB, CBNE, GROL
Senior Member, Society of Broadcast Engineers
Western Communications LLC
Cellular Phone 503-706-6506
 

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The TK-690 come in 3 band splits, you can find the info on the web if you search for it - it's part of the radio model number on the tag - knowing what split you have is a good thing - so, no, they do not cover the whole of low-band top-to-bottom.

I have modded three of these upper-split radios into the 6m band, in the last few months - they work well if you take the time to follow the VCO and front end instructions.? Programming isn't much fun either, but they do work after you are done.


On 3/1/2025 3:31 PM, Chris Boone WB5ITT via groups.io wrote:
No.... The front end can't tune that far. The TK6110 can provided you get the right band split.. I can't recall if it's the low version or the high version that can be modified for entire 10 and 6?

Chris WB5ITT?

On Sat, Mar 1, 2025, 1:21 PM MICHAEL MAY via <may2142=[email protected]> wrote:
John,
?
?Nice revision to the conversion.
?
Another unrelated TK690 question.
?
Does the TK690 also cover 10 and 6 in one radio?
?
Over the past 15 years I have read conflicting information on this and I have even seen some indication of a special programming file to enable 10 and 6 meters in one radio but I have never talked to anyone with a TK690 who can confirm if it's true.
-- 
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Adam T. Cately CETsr
      KB8MDF       
- - - - - - - - - - -
 

They are IF based like the Midlands iirc...they work damn great...Micor, etc of course had a second AM wideband strip using the RF input...they worked ok but on strong signals, I found they caused more issues..iirc there was a circuit in the extender to shut it down when channel signal strength reached a certain level ..but I saw Micor base station break into oscillation and smother a strong on channel signal, turn the extender off and the signal was back...yet a GE Master 2 on the same antenna kept on working. Later GEs like the Delta used IF based blanking with an optional plug in delay board to.allow the blanker to fire as the delayed signal reached the gates..

Chris WB5ITT?


On Sat, Mar 1, 2025, 3:16 PM John Mackey via <john=[email protected]> wrote:
Chris Boone - how dose the noise blanker in those radios compare to the Motorola Extender (such as Micor or Syntor)?

**
John Mackey, KS?F
CPBE-8VSB-DRB, CBNE, GROL
Senior Member, Society of Broadcast Engineers
Western Communications LLC
Cellular Phone 503-706-6506
 

Hi Michael,
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The TK690H comes in 3 splits for low band:
K:29.7-37.0? K2:35.0-43.0? K3: 40.0-50.0? ? The K is on the label only for those radios with Serial number starting with a letter A or letter B. For the older radios you need to go by the FCC number on the label. The K2 split ends with .......120, the K3 split ends with FCC number ending in.....130.
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I have not heard of expanding down to 10 Meters with the TK690H, just the TK6110
radios, and even then the TK6110 RX sensitivity really suffers as the varactor tracking gets way off. However, the Motorola SyntorX-X9000 will do both 10M and 6 M and everything in between quite well. On the Motorola, if 6M is set for 100W, and current limit set to below 20 A, then only 75 W out on 10 meters, but RX sensitivity OK on 10 meters, because instead of Varactor tuning, the X used a low pass and high pass filter to set band edges on the wide band? pre-amp before the balanced mixer..
?
John

On 03/01/2025 2:21 PM EST MICHAEL MAY via groups.io <may2142@...> wrote:
?
?
John,
?
?Nice revision to the conversion.
?
Another unrelated TK690 question.
?
Does the TK690 also cover 10 and 6 in one radio?
?
Over the past 15 years I have read conflicting information on this and I have even seen some indication of a special programming file to enable 10 and 6 meters in one radio but I have never talked to anyone with a TK690 who can confirm if it's true.

 

I have put 2 of the low-split Kenwood TK-690H radios into 10-meters. ? You have to program them the same way as the 6m versions putting valid frequencies into the code plug then using a program like hex workshop to change them to amateur frequencies.
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i didn’t have any problems getting the VCO to lock so I left it unmodified. ?All I really did was align the front end for maximum sensitivity. ?If you’re staying on 29.520 and above, you’re really not too far out of band on the low split radios.
 

John, FYI, I wrote a program to take any 30.xx frequency and changes it to 29.xx MHz. It does the same for 40.xxx to 43.yyy and changes its to 50.xxx to 53.yyy MHz.?
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I bet you do the same when hex editing? My program checks every location and works with the TK-690 and TK6110/TK190 software files.
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The famous Skip (is a Ham) did tell me he was able to take the TK6110-2 and make it work on 10 & 6m at the same time. From what I recall, there's no problem with the xmit, but the receiver needs allot of adjustment work detuning the frequencys in between. At the end, he was able to get decent sensitivity on 6m, but 10m was a little deaf.?
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-Pete N2MCI?
 

Hi Pete,
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I just modified Roger's TK690H code plug with all 6M frequencies re-arranged again over several groups, as I am a computer dummy, but learning!?
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John

On 03/02/2025 6:38 PM EST Pete D via groups.io <peten2mci@...> wrote:
?
?
John, FYI, I wrote a program to take any 30.xx frequency and changes it to 29.xx MHz. It does the same for 40.xxx to 43.yyy and changes its to 50.xxx to 53.yyy MHz.?
?
I bet you do the same when hex editing? My program checks every location and works with the TK-690 and TK6110/TK190 software files.
?
The famous Skip (is a Ham) did tell me he was able to take the TK6110-2 and make it work on 10 & 6m at the same time. From what I recall, there's no problem with the xmit, but the receiver needs allot of adjustment work detuning the frequencys in between. At the end, he was able to get decent sensitivity on 6m, but 10m was a little deaf.?
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-Pete N2MCI?

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