开云体育

Thanks Ruud,
Congratulations with your CW QSOs. A fantastic achievement!
I will keep your hints and tips in mind when I continue to

I will start shielding the driver and make the trifilair coil.
You mentioned 'decoupling' ; did you do this by adding RF chokes?

Bye
Ron
pa2rf


Ruud Jongeling <pe2bs@t...> wrote:

Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start oscillating
when set at a higher bias-level.' I had that problem too. In mine
BITX-PSK it was not enough to lower the bias-level. The PA seems to
work OK when I was tuning from the computer and there was no output
when there was no modulation. Unfortunately the PA worked in class C.
The whole problem turned out to be an instability in the
driver==>PA==>antenna system. I solved it the way I discribed in
my message a few weeks ago:
First I biased the IRF 510: with no modulation and carrier nulled by
the trimpot of the balanced modulator, the Id should be about 80 mA.
(from: "A simple SSB tranceiver" by Ashar Farhan www.antentop.bel.ru/)
Second: a lot of decoupling.
Third: shielding the driver stage (see picture in the picture box
PE2BS)
Fourth: change the impedance matching between driverstage and PA and
between the PA and the pi filter. Make it trifilair instead of
bifilair (see the remarks of Chris in the filebox Modifications). The
result is also more watts RF.

Now the rig is working OK. When there is no modulation, there is no
output in the SWR meter and a little on the spectrumanalyzer. Even
with mismatching the system to the antenna the PA does not generate.

It is the first HF-QRP rig I build and the results are amazing. In CW
(Hamscope and CWget on the computer) and only 5 watt I worked UA3,
YO, ER, HA!

Succes and like to hear from you.

73

Ruud
PE2BS

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks for reply Chris,
Ja in de Zoetermeerse polder waren (kei) harde signalen in de 17 m

band te horen!

I think your 6 Watts RF should be fine for digimode use. Or am i

wrong?

I hope to experience this myself on short notice. Yesterday did

first trials with the IRF510 endstage. I had 4 Watts RF out with a
RTTY test signal connected. Hope to increase output level with a few
Watts (increase supply voltage and adjust pi-filter) and do some real
trials (hopefully 2-way comms) this weekend. Found that the IRF510
has a tendency to start oscillating when set at a higher bias-level.
Should fix that too. Also found that my (bureau) desk-light when 30
cm above the VFO gets this VFO change frequency; but when Huff and
Puff circuit is connected, VFO frequency is corrected in a quick and
fine way..

My appreciation for the BITX is growing ...
Bye
Ron 73
PA2RF

vdberghak <vdberghak@z...> wrote:

Hi,
responding to the messages below:
- Ron, in the Netherlands, I heard also several stations with very
strong signals, form Russia but also from the States.
However, the 6 watt I have on 17 mtr is a bit little in combination
with my sloping dipole. Stations in (for example) Bulgaria are
answering: 'only outside Europe'....
- Rahul, I use a small 8 Ohm speaker (removed from an old

transistor

radio). When I connect the antenna, a loud noise is comming out of
the speaker. When I receive a weak station, it is just above the
noise but at the moment a strong station enters, I really have to
turn down the volume potmeter immidiatly!
In fact, the volume is never on its maximum.
By the way, I use the real, original BC107, metal can ;-) For the
stage before the LM386 I use a BC109.
Best regards,
Chris.

Interesting are you using a speaker or heaphone. Secondly what

transistors are you usingBC547s or 2n3904s

73
Rahul VU3WJM

Bye the way, RX signals on 17m were fine this afternoon, heard

ssb

voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire

antenna

connected. Some signals clear enough to decode...
Does anybody have experience with one wave-length antennas (up

till

now I have only used half or quarter lambda ant's..)

Bye bye and have a good Easter weekend (for what's left)
Ron
PA2RF

Yahoo! Groups SponsorADVERTISEMENT


---------------------------------
Yahoo! Groups Links

To visit your group on the web, go to:


To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around

Yahoo! Groups SponsorADVERTISEMENT


---------------------------------
Yahoo! Groups Links

To visit your group on the web, go to:


To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.



---------------------------------
Do you Yahoo!?
Yahoo! Small Business - Try our new resources site!