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I finished the 80 meter beacon last weekend and had a few problems. I first
destroyed a few 2N7000s by turning R8 fully counter clockwise instead of
clockwise - read the directions!!

Then I could not get the oscillator above 3500.540. I changed turns on L1
several times and finally ended shorting it but could not get above 3500.60.
I then changed C9 from a 5 - 25 pf to a 3 to 16 pf. Now I can go up to
3500.860. I think the issue is a finicky xtal.

Let me know when you "see me". I currently have my 70 mw beacon on 3500.850
(as close to mid band as I can adjust)



Ken Evans, W4DU
QRP ARCI 696, GQRP 5918, FP 295, NOGA, ARRL Life

--- In QRPLabs@..., "Ken Evans" <w4du@...> wrote:

I finished the 80 meter beacon last weekend and had a few problems. I first
destroyed a few 2N7000s by turning R8 fully counter clockwise instead of
clockwise - read the directions!!

Then I could not get the oscillator above 3500.540. I changed turns on L1
several times and finally ended shorting it but could not get above 3500.60.
I then changed C9 from a 5 - 25 pf to a 3 to 16 pf. Now I can go up to
3500.860. I think the issue is a finicky xtal.

Let me know when you "see me". I currently have my 70 mw beacon on 3500.850
(as close to mid band as I can adjust)

Hi Ken

I built an 80m kit today and had the same problem with the oscillator
being too low. The only trimmer caps I had to hand wouldn't go low
enough so I used a "gimmick" cap same as the coupling to the LED and
have managed to get the frequency up to around 850.

I was able to get 100mW output but when switching off the TX and on
again the oscillator wouldn't start until I backed off R6, this gave
me an output of 70mW and a reliable start up, (I'm powering mine from
a 4.8V supply).

I had a problem with these low profile xtals when trying to make up
a 30m TX (not a QRPLabs one) only in that case the frequency was way
too high and wouldn't pull down.

I wonder how the other folk have got on with their 80M kits, your
post is the only one I've seen about the problem we've both had.

73 Les G3VYZ

--- In QRPLabs@..., "g3vyz" <Les@...> wrote:

--- In QRPLabs@..., "Ken Evans" <w4du@> wrote:

I finished the 80 meter beacon last weekend and had a few problems. I first
destroyed a few 2N7000s by turning R8 fully counter clockwise instead of
clockwise - read the directions!!

Then I could not get the oscillator above 3500.540. I changed turns on L1
several times and finally ended shorting it but could not get above 3500.60.
I then changed C9 from a 5 - 25 pf to a 3 to 16 pf. Now I can go up to
3500.860. I think the issue is a finicky xtal.

Let me know when you "see me". I currently have my 70 mw beacon on 3500.850
(as close to mid band as I can adjust)

Hi Ken

I built an 80m kit today and had the same problem with the oscillator
being too low. The only trimmer caps I had to hand wouldn't go low
enough so I used a "gimmick" cap same as the coupling to the LED and
have managed to get the frequency up to around 850.

I was able to get 100mW output but when switching off the TX and on
again the oscillator wouldn't start until I backed off R6, this gave
me an output of 70mW and a reliable start up, (I'm powering mine from
a 4.8V supply).

I had a problem with these low profile xtals when trying to make up
a 30m TX (not a QRPLabs one) only in that case the frequency was way
too high and wouldn't pull down.

I wonder how the other folk have got on with their 80M kits, your
post is the only one I've seen about the problem we've both had.

That should have been R8 not R6 :-(

Today I got a 1.5 to 5pF ceramic trimmer for C9 instead of the
supplied 25pF, now I can tune up to just above 7000.900KHz and
setting the TX frequency between 800 to 900 is reasonably easy.

Les G3VYZ

--- In QRPLabs@..., "g3vyz" <Les@...> wrote:

Today I got a 1.5 to 5pF ceramic trimmer for C9 instead of the
supplied 25pF, now I can tune up to just above 7000.900KHz and
setting the TX frequency between 800 to 900 is reasonably easy.

I'm not doing very well today :-( that should say 3500.900KHz not
7MHz.

My latest 7MHz MEPT is under construction now to be followed by
one for 30m in the next day or so.

During off and on air testing over the past 24 hours I've been
pleasantly surprised at how stable the transmit frequency has been.

Les G3VYZ