|
Hello,
I am having trouble getting power out on 2M (using it as a beacon).
I see 200mv on the collector of the BS170 fet with 5V on the drain.
I peaked the output adjusting the bias, for a clean looking signal on the scope.
Am I supposed to use +12V on the U3S PA+ line?
The 5W PA does amplify the signal, but I fear the drive power is too low.
I do have the VHF fet in the 5W PA board.
This is my first U3S unit.? I am monitoring the unit on a 2M receiver, so I know it is
transmitting, plus looking on a scope.? No power indication on a 15W wattmeter, maybe
the needle just barely moves.
Things to check?
TIA
73
Glen K4KV
|
I am having trouble getting power out on 2M (using it as a beacon).
Glen, I'm not aware much has been said about 2m operation. I see 200mv on the collector of the BS170 fet with 5V on the drain.
200mv on the gate? I'd expect it should be higher but capacitance must be high for 2m. Are your scope and probes good for 2m? I peaked the output adjusting the bias, for a clean looking signal on the scope.
I thought the bias was adjusted to the point that the FET just begins to take current. You do not say where you look on your scope but it is squarish waves around the FET. Not until after the LPF will it look clean. Sorry, that's about all I can say. 73 Alan G4ZFQ Am I supposed to use +12V on the U3S PA+ line?
The 5W PA does amplify the signal, but I fear the drive power is too low.
I do have the VHF fet in the 5W PA board.
|
Hi Glen
It's been some years since I tried a U3S on 2m. It was before the change to the bifilar output transformer. It could be worth trying it also with a single winding inductor.
My power output was 14mW (zero idle current adjustment) and could be pushed to 17mW with higher gate bias.
As Alan said - do you believe your scope and probes? If a 'scope is what you used? You'd need a pretty good setup to get any decent accuracy on 2m. In my case I used a spectrum analyzer for the measurement and I was reasonably confident in it.
73 Hans G0UPL? ?
> I am having trouble getting power out on 2M (using it as a beacon).
>
Glen,
I'm not aware much has been said about 2m operation.
> I see 200mv on the collector of the BS170 fet with 5V on the drain.
>
200mv on the gate? I'd expect it should be higher but capacitance must
be high for 2m. Are your scope and probes good for 2m?
> I peaked the output adjusting the bias, for a clean looking signal on
> the scope.
>
I thought the bias was adjusted to the point that the FET just begins to
take current. You do not say where you look on your scope but it is
squarish waves around the FET. Not until after the LPF will it look clean.
Sorry, that's about all I can say.
73 Alan? G4ZFQ
> Am I supposed to use +12V on the U3S PA+ line?
>
> The 5W PA does amplify the signal, but I fear the drive power is too low.
>
> I do have the VHF fet in the 5W PA board.
|
Hans,
Wow, that is pretty low output!? I think the VHF fet in the 5W PA
needs 50mw for
adequate drive.
Well, thanks for the reply, but what about the +V for the U3S
supply, should I use +12V ???
I already figured the components on the U3S for 2M were not
adequate.? I changed the inductor
feeding the BS170 drain to around 450nH, then changed the caps
involved to 0.001uf instead of
0.1uf.? A friend told me he made up a U3S for another guy on 2M.?
He never mentioned any mods to
be done.
Regarding the scope, well it is a 100Mhz Rigol, but shows a
pretty decent signal on 2M.? I was able to
see some clipping when adjusting the bias, so backed off until it
looked clean.? Sounds good on the 2M
rx...
73
Glen K4KV
On 8/9/2018 01:41, Hans Summers wrote:
toggle quoted message
Show quoted text
Hi Glen
It's been some years since I tried a U3S on
2m. It was before the change to the bifilar output
transformer. It could be worth trying it also with a single
winding inductor.
My power output was 14mW (zero idle current
adjustment) and could be pushed to 17mW with higher gate
bias.
As Alan said - do you believe your scope and
probes? If a 'scope is what you used? You'd need a pretty
good setup to get any decent accuracy on 2m. In my case I
used a spectrum analyzer for the measurement and I was
reasonably confident in it.
73 Hans G0UPL?
?
> I
am having trouble getting power out on 2M (using it as a
beacon).
>
Glen,
I'm not aware much has been said about 2m operation.
> I see 200mv on the collector of the BS170 fet with 5V
on the drain.
>
200mv on the gate? I'd expect it should be higher but
capacitance must
be high for 2m. Are your scope and probes good for 2m?
> I peaked the output adjusting the bias, for a clean
looking signal on
> the scope.
>
I thought the bias was adjusted to the point that the FET
just begins to
take current. You do not say where you look on your scope
but it is
squarish waves around the FET. Not until after the LPF
will it look clean.
Sorry, that's about all I can say.
73 Alan? G4ZFQ
> Am I supposed to use +12V on the U3S PA+ line?
>
> The 5W PA does amplify the signal, but I fear the
drive power is too low.
>
> I do have the VHF fet in the 5W PA board.
|
Hi Glen? Wow, that is pretty low output!? I think the VHF fet in the 5W PA
needs 50mw for
adequate drive.
Well, thanks for the reply, but what about the +V for the U3S
supply, should I use +12V ???
My 14mW (and higher 17mW) were with 5V supply. I guess you may get a little more with 12V supply to the BS170. Use only ONE BS170, not more - more will have too much capacitance when in parallel, which will make things worse.
I already figured the components on the U3S for 2M were not
adequate.? I changed the inductor
feeding the BS170 drain to around 450nH, then changed the caps
involved to 0.001uf instead of
0.1uf.? A friend told me he made up a U3S for another guy on 2M.?
He never mentioned any mods to
be done.
My 14mW was measured without any modifcations being done. A standard U3S with a 25-turn L1 inductor (not the bifilar transformer which was a later modification).?
Regarding the scope, well it is a 100Mhz Rigol, but shows a
pretty decent signal on 2M.? I was able to
see some clipping when adjusting the bias, so backed off until it
looked clean.? Sounds good on the 2M
rx...
I do not think you can trust the amplitude reading of a 100MHz 'scope (and its probes) when you are measuring 2m (145MHz). I would personally start stopping to trust it at even lower than 100MHz...
73 Hans G0UPL
|
I built my U3A for two meters about 2 years ago now and I opted to use a replacement to the BS170 that has a much higher Ft… I don’t recall what I used off-hand but it puts out much more power than the BS170.? As I recall the equivalent Ft for the BS170 is about 100MHz (although I could be wrong because this is all by memory).? Even a 2N3866 silicon NPN has an Ft of 800MHz… and you can scan the parts catalog for a MOSFET that has an Ft in the 500+MHz range that would be a better choice.? Nothing against the BS170… it’s a great little switch, but it just gives up the ghost a bit above 100惭贬锄… ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? Moderator – North American QRO Group at Groups.IO. ? email:? bill@... ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Info
Sent: Thursday, August 9, 2018 5:17 AM
To: [email protected]
Subject: Re: [QRPLabs] U3S /5W PA on 2M? Hans, Wow, that is pretty low output!? I think the VHF fet in the 5W PA needs 50mw for adequate drive. Well, thanks for the reply, but what about the +V for the U3S supply, should I use +12V ??? I already figured the components on the U3S for 2M were not adequate.? I changed the inductor feeding the BS170 drain to around 450nH, then changed the caps involved to 0.001uf instead of 0.1uf.? A friend told me he made up a U3S for another guy on 2M.? He never mentioned any mods to be done. Regarding the scope, well it is a 100Mhz Rigol, but shows a pretty decent signal on 2M.? I was able to see some clipping when adjusting the bias, so backed off until it looked clean.? Sounds good on the 2M rx... ? 73 Glen K4KV ? ? On 8/9/2018 01:41, Hans Summers wrote: Hi Glen It's been some years since I tried a U3S on 2m. It was before the change to the bifilar output transformer. It could be worth trying it also with a single winding inductor. My power output was 14mW (zero idle current adjustment) and could be pushed to 17mW with higher gate bias. As Alan said - do you believe your scope and probes? If a 'scope is what you used? You'd need a pretty good setup to get any decent accuracy on 2m. In my case I used a spectrum analyzer for the measurement and I was reasonably confident in it. ? > I am having trouble getting power out on 2M (using it as a beacon).
>
Glen,
I'm not aware much has been said about 2m operation.
> I see 200mv on the collector of the BS170 fet with 5V on the drain.
>
200mv on the gate? I'd expect it should be higher but capacitance must
be high for 2m. Are your scope and probes good for 2m?
> I peaked the output adjusting the bias, for a clean looking signal on
> the scope.
>
I thought the bias was adjusted to the point that the FET just begins to
take current. You do not say where you look on your scope but it is
squarish waves around the FET. Not until after the LPF will it look clean.
Sorry, that's about all I can say.
73 Alan? G4ZFQ
> Am I supposed to use +12V on the U3S PA+ line?
>
> The 5W PA does amplify the signal, but I fear the drive power is too low.
>
> I do have the VHF fet in the 5W PA board.
?
|
Bill,
I thought as much...will search for a better part.? I sure wish
someone would publish the mods
for 2M!!!
73
Glen K4KV
On 8/9/2018 09:28, J68HZ wrote:
toggle quoted message
Show quoted text
I
built my U3A for two meters about 2 years ago now and I
opted to use a replacement to the BS170 that has a much
higher Ft… I don’t recall what I used off-hand but it puts
out much more power than the BS170.? As I recall the
equivalent Ft for the BS170 is about 100MHz (although I
could be wrong because this is all by memory).? Even a
2N3866 silicon NPN has an Ft of 800MHz… and you can scan the
parts catalog for a MOSFET that has an Ft in the 500+MHz
range that would be a better choice.? Nothing against the
BS170… it’s a great little switch, but it just gives up the
ghost a bit above 100惭贬锄…
?
?
Dr.
William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ
VP5/K9HZ PJ2/K9HZ
?
Owner
- Operator
Big
Signal Ranch – K9ZC
Staunton,
Illinois
?
Owner –
Operator
Villa
Grand Piton – J68HZ
Soufriere,
St. Lucia W.I.
Rent it:
Like us on Facebook!
?
Moderator
– North American QRO Group at Groups.IO.
?
email:?
bill@...
?
?
?
Hans,
Wow, that is pretty low output!? I think the VHF fet in the
5W PA needs 50mw for
adequate drive.
Well, thanks for the reply, but what about the +V for the U3S
supply, should I use +12V ???
I already figured the components on the U3S for 2M were not
adequate.? I changed the inductor
feeding the BS170 drain to around 450nH, then changed the
caps involved to 0.001uf instead of
0.1uf.? A friend told me he made up a U3S for another guy on
2M.? He never mentioned any mods to
be done.
Regarding the scope, well it is a 100Mhz Rigol, but shows a
pretty decent signal on 2M.? I was able to
see some clipping when adjusting the bias, so backed off
until it looked clean.? Sounds good on the 2M
rx...
?
73
Glen K4KV
?
?
On 8/9/2018 01:41, Hans Summers wrote:
Hi Glen
It's been some years since I tried
a U3S on 2m. It was before the change to the bifilar
output transformer. It could be worth trying it also
with a single winding inductor.
My power output was 14mW (zero idle
current adjustment) and could be pushed to 17mW with
higher gate bias.
As Alan said - do you believe your
scope and probes? If a 'scope is what you used? You'd
need a pretty good setup to get any decent accuracy on
2m. In my case I used a spectrum analyzer for the
measurement and I was reasonably confident in it.
?
>
I am having trouble getting power out on 2M (using
it as a beacon).
>
Glen,
I'm not aware much has been said about 2m operation.
> I see 200mv on the collector of the BS170 fet
with 5V on the drain.
>
200mv on the gate? I'd expect it should be higher
but capacitance must
be high for 2m. Are your scope and probes good for
2m?
> I peaked the output adjusting the bias, for a
clean looking signal on
> the scope.
>
I thought the bias was adjusted to the point that
the FET just begins to
take current. You do not say where you look on your
scope but it is
squarish waves around the FET. Not until after the
LPF will it look clean.
Sorry, that's about all I can say.
73 Alan? G4ZFQ
> Am I supposed to use +12V on the U3S PA+ line?
>
> The 5W PA does amplify the signal, but I fear
the drive power is too low.
>
> I do have the VHF fet in the 5W PA board.
?
|
Me too Glen!
I'm quite interested in the subject of using the U3S on 2 meters and
would welcome any information on mods, upgrades, etc. with that in
mind. I am following your thread here closely to see what it might
turn up.
I'm somewhat lost now as I have never seen Ft listed on a switching
FET datasheet. I can only guess Bill means to use a linear RF rated
FET, but as they are very different beasts I worry about trying to
retrofit on into a U3S without knowing what I'm doing.
73,
Paul N1BUG
toggle quoted message
Show quoted text
On 08/09/2018 10:58 AM, Info wrote: Bill,
I thought as much...will search for a better part.? I sure wish
someone would publish the mods
for 2M!!!
73
Glen K4KV
On 8/9/2018 09:28, J68HZ wrote:
I built my U3A for two meters about 2 years ago now and I opted to
use a replacement to the BS170 that has a much higher Ft… I don’t
recall what I used off-hand but it puts out much more power than
the BS170.? As I recall the equivalent Ft for the BS170 is about
100MHz (although I could be wrong because this is all by memory).?
Even a 2N3866 silicon NPN has an Ft of 800MHz… and you can scan
the parts catalog for a MOSFET that has an Ft in the 500+MHz range
that would be a better choice.? Nothing against the BS170… it’s a
great little switch, but it just gives up the ghost a bit above
100惭贬锄…
|
Hi Paul,
I have a U3S with OCXO and 5watt PA running on 2m.
Mods are;
1) Single BS170 U3S PA with single turn toroid (not trifilar).
2) BS170 PA running at 9volts. Output connection to LPF cut and connected directly to 5watt PA input (no LPF). Bias set for this device max out then backed off a little to prevent overheat. I always have small heat sink on these devices too.
3) RD15VF1 device on the 5watt PA (note different pin layout instructions). SINGLE turn 10turn toroid (not trifilar as supplied).
4) Po from 5watt via fed back to 2m LPF input (and relay switched board in my case).
4) Bias set on this device for just taking a few mA with no RF drive.
5) 13.5 volts to 5 watt PA.
6) In menu, SHAPING set to 10? 140.
7)? Po = 0.5 watts on 144MHz.
Warning, heat from the PA will cause frequency drift. You need to physically separate them, and maybe try a few other frequency stabilising tricks as well.
73 Ken G4APB
|
Sorry, that should say single WIND toroids, not single turn!!
Ken G4APB
|
Ken,
You are saying 0.5W out of the 5W PA board?
That is not acceptable.? I have that same fet on my Ukrainian
transverter, and get nearly 10W out
of it.
I will order a 'proper' fet for the U3S.? I agree that the 5W PA
transformer is wrong for 2M.
You did not mention it, but all the caps involved with the
circuit should not be 0.1uf.? I changed
mine to 1000pf.? Even the one from the synthesizer.
73
Glen K4KV
On 8/10/2018 05:35, KEN G4APB via
Groups.Io wrote:
toggle quoted message
Show quoted text
Sorry, that should say single WIND toroids, not single turn!!
Ken G4APB
|
On 10/08/2018 10:50, Info wrote:
Ken,
You are saying 0.5W out of the 5W PA
board?
That is not acceptable.?
It's perhaps more acceptable when put into the correct context.
How is the PA Kit advertised on the QRP Labs site?
5W HF PA
It can be used as the basis for you to modify, change and
experiment, changing the surrounding RF de/coupling capacitors
& inductors & PA device to allow use at VHF.
Alan
I have that same fet on my Ukrainian transverter, and get
nearly 10W out
of it.
I will order a 'proper' fet for the U3S.? I agree that the 5W
PA transformer is wrong for 2M.
You did not mention it, but all the caps involved with the
circuit should not be 0.1uf.? I changed
mine to 1000pf.? Even the one from the synthesizer.
73
Glen K4KV
On 8/10/2018 05:35, KEN G4APB via
Groups.Io wrote:
Sorry, that should say single WIND toroids, not single turn!!
Ken G4APB
|
Yes, 0.5W is all I managed to achieve out of the '5 watt' PA. Was more 'acceptable' than the 20mW barefoot that I was getting before I added the PA.
I did try a 2N4427 driver instead of the BS170 and got almost 1 watt out but it (2n4427) overheated and blew during experiments. I have not changed any caps. There comes a point in experimentation when I stop and just use the kit.?
If anyone can do better, lets hear from them...
73 Ken G4APB
|
Hi Ken,
Not better, different.
?Thinking about easy access to VHF PA's rather than starting from
scratch.
Strip the driver & PA PCB's from a High Band Pye W15 Westminster
PMR radio.
Don't pay more than ?10 from a rally, unwanted & unloved because
they are Xtal controlled RX / TX
All modular, the PA RF design development done for me. Proper
components, I'm biased it's my vintage.
Also "free" in the sub ?10 price is a ready built low power exciter
TX strip for a club fox hunt project courtesy of a ProgRock kit?
And a full RX strip, pretty good front end compared to a current
Yaesu Fusion repeater in a box, ask one of the repeater groups about
real life "progress" when placed at a RF congested site....
If feeling nostalgic? get a bootmount Westminster W30, QQV06/40
bottle in the PA and you can hacksaw the HT inverter from the
chassis so the power requirement is a 12v shack standard.
There must be similar land mobile equipment available cheaply
world wide to do something similar.
Alan
On 10/08/2018 12:19, KEN G4APB via
Groups.Io wrote:
toggle quoted message
Show quoted text
Yes, 0.5W is all I managed to achieve out of the '5 watt' PA. Was
more 'acceptable' than the 20mW barefoot that I was getting before
I added the PA.
I did try a 2N4427 driver instead of the BS170 and got almost 1
watt out but it (2n4427) overheated and blew during experiments. I
have not changed any caps. There comes a point in experimentation
when I stop and just use the kit.?
If anyone can do better, lets hear from them...
73 Ken G4APB
|
Hi Ken,
Thanks for the information on your VHF mods. I was going to ask if
you measured power out of the BS170 but I believe you answered that
here. I assume 20 mW is with 9V.
There are RF power modules available that will amplify 20 mW to 7W.
At least one is in the 25 USD price class. These might be worth
looking at as a PA option.
When I get caught up on the backlog of projects I plan to buy
another U3S for VHF use. My present unit is dedicated to LF and I
don't want to mess with it.
73,
Paul N1BUG
toggle quoted message
Show quoted text
On 08/10/2018 07:19 AM, KEN G4APB via Groups.Io wrote: Yes, 0.5W is all I managed to achieve out of the '5 watt' PA. Was
more 'acceptable' than the 20mW barefoot that I was getting before I
added the PA.
I did try a 2N4427 driver instead of the BS170 and got almost 1 watt
out but it (2n4427) overheated and blew during experiments. I have
not changed any caps. There comes a point in experimentation when I
stop and just use the kit.?
If anyone can do better, lets hear from them...
73 Ken G4APB
|
J68HZ
N1BUG
Alan de G1FXB