Re: Measuring Resonant Frequency of Traps Newbies SSTV
I don't know about you guys but when I first got
a Technician license 21 years ago (after passing 5WPM CW) and I
was finally allowed to use a 2 meter HT I
could not purchase a 2 meter HT for anything less
than $150.
That $150 was cost prohibitive for me back then.
Over time I observed a number of other hams who were in the same
financial position... raising kids... who could not justify
blowing $150 on an HT for the hobby.
BUT
now that BAOFENG UV5R costs around $30.......
it just seems to me that this 2 meter HT would be a great
stepping stone to indroduce newbies to the hobby of ham radio.
And the WLN and BAOFENG 888s 440 radios are even cheaper.
I pretty much live on a $15 HT now.
Just mind blowing that my first HT cost ten times as much as this
one I use now....
and
I had to drive 3 hours to go buy my first HT at HRO in Delaware.
SO
then what?
Newbie....?? FNG ....?? has an HT.....? and asks what else he can
do in the hobby... having JUST that one $30 radio.
?PSK31 .....HELLSHREIBER and anything else you want to blast out
of FLDIGI.... and SSTV and ? APRS .....
all work fine with BAOFENGs .....
teach them how to build an interface..... NOT BUY... an
interface....
and the hobby will no longer be a repeater hobby.
73 Rob KB3BYT
On 12/18/2019 08:01 PM, k6whp wrote:
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It's a
Military/Viet Nam Era thing. "F---ing New Guy" meaning the newest
arrival in a unit.
Also, many, many thanks for the great ideas. I think with the
availability and affordability of the antenna analyzers (starting
from ~$50 for the Cheap Chinese? ones) and the $20 component
checkers or the Chinese L/C meters, that's a viable solution and
can easily be argued as a "must have" for the Baofeng Techs who
want to branch out and actually learn about antenna and
electronics principles.?
I sure wish I has that kind of stuff when I started out as a
Novice in 1961!
Again, thank you all for the robust (and informative)
responses! And, by the way, thanks Ryan for the great forum.
It's really running great!
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got
worse."
|
Loading the clock outputs with 50 ohms (such as a 6db attenuator) will make crosstalk and phase noise much worse. Hence the discussion here of cheap 74ACT and 74LVC series buffers to drive a 50 ohm load. Hans reports the Si5351 based QCX does pretty good on phase noise, see the last paragraph here: ? ?? /g/qrptech/message/326Apparently much better than a traditional VFO. If you need better than that for some reason, SiLabs does sell parts that cost more than $1. Jerry
On Wed, Dec 18, 2019 at 02:08 PM, Bo, OZ2M wrote:
Hi
Yes, generally it is a good idea to make the mixer see a constant load vs frequency. So a 6 dB pad will provide a higher return loss than 3 dB will. But given that the output power from a single CLKx pin is ~11 dBm a 3 dB to 4 dB is all the headroom there is for a 7 dBm DBM.
For us radio amateurs spurious matters. To many a simple low pass filter following the Si5351A is fine ¨C ¡°Spectrum, you ask? I have added a LPF so everything is honky dory¡±. Harmonics are easy to do something about. But what about the receivers, that may be affected by bad phase noise and spurious? Karen, RA3APW, has documented his Si5351A spectrum findings here you can try to compare them with a different implementation like the RFzero: where cross-talk doesn¡¯t see to be an issue either.
So just mounting a Si5351A on a piece of PCB doesn¡¯t necessarily mean that it will be a good solution RF-wise. The Si5351A is a device designed for the digital domain where spurious is close to being irrelevant as long as it doesn¡¯t affect the ability to lock/trigger on a stable signal, so jitter, i.e. phase noise, matters.
Bo
|
Re: Measuring Resonant Frequency of Traps
It's a Military/Viet Nam Era thing. "F---ing New Guy" meaning the newest arrival in a unit.
Also, many, many thanks for the great ideas. I think with the availability and affordability of the antenna analyzers (starting from ~$50 for the Cheap Chinese? ones) and the $20 component checkers or the Chinese L/C meters, that's a viable solution and can easily be argued as a "must have" for the Baofeng Techs who want to branch out and actually learn about antenna and electronics principles.?
I sure wish I has that kind of stuff when I started out as a Novice in 1961!
Again, thank you all for the robust (and informative) responses! And, by the way, thanks Ryan for the great forum. It's really running great!
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
Re: Measuring Resonant Frequency of Traps
whats the FNG mean?
On 12/18/2019 04:12 PM, Eric KE6US
wrote:
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Show quoted text
Did we miss the part where William explains
they are FNG Baofeng techs?
Eric KE6US
On 12/18/2019 1:02 PM, Jerry Gaffke
via Groups.Io wrote:
Or, obviously,
just a transmitter with an SWR meter (perhaps Diz's tandem
match).
But the single number representing SWR into an assumed 50 ohm
antenna system
is not nearly as informative as the two numbers for complex
impedance (resistance and capacitive/inductive reactance)
that the nanoVNA can tell you.
On Wed, Dec 18, 2019 at 11:40 AM, Jerry Gaffke wrote:
Perhaps an si5351 and Diz's Tandem Match would get
you most of the way there?
? ??
Useful for other things once the antenna is trimmed.
|
Re: Measuring Resonant Frequency of Traps
NOTHING beats a real antenna analyzer.
Just my opinion.
I bought a used MFJ259 for $100 ....twenty years
ago and it has been THE "go to" tool for the local radio club
and
has been passed around so much it got the power
supply jack damaged and needs to be repaired.
So... when I recently learned about the nanoVNA
being able to to the same thing I use the MFJ259 for.....
hand craft HF antennas......
I jumped on that nanoVNA.... its "in the mail"....
so
I highly recommend that you get a couple guys to
chip in and buy the nanoVNA for around $50
if you can't afford one for yourself.
The MFJ259 ...and that line up ...?
are great tools but if you NEVER are going to
play with ALL the frequencies they off .... then why spend
another $400 on a tool you will never use.
The MFJ213 is the HF version... costs $230.
You KNOW we all would own these tools if they
ware not so expensive.
So check out the nanoVNA.
73 Rob KB3BYT
/18/2019 01:51 PM, k6whp wrote:
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Thought I'd
throw this out for the group. I got trapped [sorry!] into
schooling some "Baofeng Techs" (FNGs) who are interested in
getting into HF about building trap antennas. Of course, being
new, they do not have the luxuriant array of test equipment we
seem to stack up over the years so I wanted to suggest to them
ways they could construct traps and prove out the resulting
resonant frequencies of same.
They will be pointed to the appropriate theory, formulas, and
internet calculators to derive the component values, inductance,
number of turns, etc. but after they have built the traps, I
wanted to provide them with a crude but decent method of
determining the resonant frequency. (It would not do, after all,
to have them wind a 20m trap resonant at 16 MHz.)?
Assume they have a brand new transceiver, can afford a decent VSWR
meter, and can lay their hands on stuff like #47 panel lights,
LEDs, wire, coax, etc. and know how to solder. They know ought of
antenna analyzers, don't have a clue what a GDO is, and other
"desert island" stuff like that.
Appreciate any ideas.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got
worse."
|
Hi
Yes, generally it is a good idea to make the mixer see a constant load vs frequency. So a 6 dB pad will provide a higher return loss than 3 dB will. But given that the output power from a single CLKx pin is ~11 dBm a 3 dB to 4 dB is all the headroom there is for a 7 dBm DBM.
For us radio amateurs spurious matters. To many a simple low pass filter following the Si5351A is fine ¨C ¡°Spectrum, you ask? I have added a LPF so everything is honky dory¡±. Harmonics are easy to do something about. But what about the receivers, that may be affected by bad phase noise and spurious? Karen, RA3APW, has documented his Si5351A spectrum findings here you can try to compare them with a different implementation like the RFzero: where cross-talk doesn¡¯t see to be an issue either.
So just mounting a Si5351A on a piece of PCB doesn¡¯t necessarily mean that it will be a good solution RF-wise. The Si5351A is a device designed for the digital domain where spurious is close to being irrelevant as long as it doesn¡¯t affect the ability to lock/trigger on a stable signal, so jitter, i.e. phase noise, matters.
Bo
|
Re: Measuring Resonant Frequency of Traps
A Millen Antenna Bridge will give you both the R and Xc of an antenna.
?
But a simple Heathkit Antenna Bridge will give you only the R of the antenna.
?
These things date WAY BACK!
?
And they have only PASSIVE? components!
?
Bob Macklin
K5MYJ
Seattle, Wa.
?
---
New Outlook Express and Windows Live Mail replacement - get it here:
? ?
?
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----- Original Message -----
Sent: 12/18/2019 1:12:20 PM
Subject: Re: [qrptech] Measuring Resonant Frequency of Traps
Did we miss the part where William explains they are FNG Baofeng techs?
Eric KE6US
On 12/18/2019 1:02 PM, Jerry Gaffke via Groups.Io wrote:
Or, obviously, just a transmitter with an SWR meter (perhaps Diz's tandem match).
But the single number representing SWR into an assumed 50 ohm antenna system
is not nearly as informative as the two numbers for complex impedance (resistance and capacitive/inductive reactance)
that the nanoVNA can tell you.
On Wed, Dec 18, 2019 at 11:40 AM, Jerry Gaffke wrote:
Perhaps an si5351 and Diz's Tandem Match would get you most of the way there?
? ??
Useful for other things once the antenna is trimmed.
|
Re: Measuring Resonant Frequency of Traps
Some newer transceivers, like the Icom IC-7300, include a graphical SWR plot function. Put a dummy load on the other end of the trap and have the radio show you the swr plot. That might help some. Mike M.? KU4QO
On Wed, Dec 18, 2019 at 1:51 PM k6whp < k6whp@...> wrote: Thought I'd throw this out for the group. I got trapped [sorry!] into schooling some "Baofeng Techs" (FNGs) who are interested in getting into HF about building trap antennas. Of course, being new, they do not have the luxuriant array of test equipment we seem to stack up over the years so I wanted to suggest to them ways they could construct traps and prove out the resulting resonant frequencies of same.
They will be pointed to the appropriate theory, formulas, and internet calculators to derive the component values, inductance, number of turns, etc. but after they have built the traps, I wanted to provide them with a crude but decent method of determining the resonant frequency. (It would not do, after all, to have them wind a 20m trap resonant at 16 MHz.)?
Assume they have a brand new transceiver, can afford a decent VSWR meter, and can lay their hands on stuff like #47 panel lights, LEDs, wire, coax, etc. and know how to solder. They know ought of antenna analyzers, don't have a clue what a GDO is, and other "desert island" stuff like that.
Appreciate any ideas.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
Re: Measuring Resonant Frequency of Traps
Did we miss the part where William explains they
are FNG Baofeng techs?
Eric KE6US
On 12/18/2019 1:02 PM, Jerry Gaffke via
Groups.Io wrote:
toggle quoted message
Show quoted text
Or, obviously, just
a transmitter with an SWR meter (perhaps Diz's tandem match).
But the single number representing SWR into an assumed 50 ohm
antenna system
is not nearly as informative as the two numbers for complex
impedance (resistance and capacitive/inductive reactance)
that the nanoVNA can tell you.
On Wed, Dec 18, 2019 at 11:40 AM, Jerry Gaffke wrote:
Perhaps an si5351 and Diz's Tandem Match would get you
most of the way there?
? ??
Useful for other things once the antenna is trimmed.
|
Re: Measuring Resonant Frequency of Traps
Or, obviously, just a transmitter with an SWR meter (perhaps Diz's tandem match).
But the single number representing SWR into an assumed 50 ohm antenna system
is not nearly as informative as the two numbers for complex impedance (resistance and capacitive/inductive reactance)
that the nanoVNA can tell you.
toggle quoted message
Show quoted text
On Wed, Dec 18, 2019 at 11:40 AM, Jerry Gaffke wrote:
Perhaps an si5351 and Diz's Tandem Match would get you most of the way there?
? ??
Useful for other things once the antenna is trimmed.
|
Re: Measuring Resonant Frequency of Traps
Might not be a good idea to test the traps in isolation.
The remainder of the antenna system can affect resonance.
|
Re: Measuring Resonant Frequency of Traps
Google "nanoVNA",? $50 for a vna good from khz to ghz.
Display is teensy and thumbswitch is cranky, but performance is exceptional.
Newer versions are coming out.
Non-trivial for the neophyte, but extremely educational.
The antuino from hfsignals would also be fine as an antenna analyzer.
Could also serve as a sort-of spectrum analyzer if you can live with the images and harmonics, it has no front end filtering.
Either one should prove a lot more interesting than spending $300 on an MFJ-259?
Anybody have other suggestions on what's new in this sort of gear?
Comments on what works?
Perhaps an si5351 and Diz's Tandem Match would get you most of the way there?
? ??
Useful for other things once the antenna is trimmed.
Jerry, KE7ER
|
Re: Measuring Resonant Frequency of Traps
Connect the parallel resonant circuit in line
with their transceiver input and tune for a null or connect it
across the input and tune for a peak. You could also have them
reconfigure it as a series resonant circuit, test it in the same
way and learn why traps are parallel resonant, not series
resonant.
For an unforgettable lifelong lesson, albeit an
expensive one, let them transmit into it. OK, maybe just a
strong warning not to ever do that would be in order.
Eric KE6US
On 12/18/2019 10:51 AM, k6whp wrote:
toggle quoted message
Show quoted text
Thought I'd
throw this out for the group. I got trapped [sorry!] into
schooling some "Baofeng Techs" (FNGs) who are interested in
getting into HF about building trap antennas. Of course, being
new, they do not have the luxuriant array of test equipment we
seem to stack up over the years so I wanted to suggest to them
ways they could construct traps and prove out the resulting
resonant frequencies of same.
They will be pointed to the appropriate theory, formulas, and
internet calculators to derive the component values, inductance,
number of turns, etc. but after they have built the traps, I
wanted to provide them with a crude but decent method of
determining the resonant frequency. (It would not do, after all,
to have them wind a 20m trap resonant at 16 MHz.)?
Assume they have a brand new transceiver, can afford a decent VSWR
meter, and can lay their hands on stuff like #47 panel lights,
LEDs, wire, coax, etc. and know how to solder. They know ought of
antenna analyzers, don't have a clue what a GDO is, and other
"desert island" stuff like that.
Appreciate any ideas.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got
worse."
|
Re: Measuring Resonant Frequency of Traps
Although it may qualify as "fancy" equipment for the "desert island" scenario, an antenna analyzer can easily show you the SWR of a filter at a given frequency, and you can manually plot a curve if you like, or else just watch the values as you go up/down in frequency to eyeball it. I do this for building/tuning band pass filters: 50ohm load on one end, analyzer on the other. Works great.
On Wed, Dec 18, 2019 at 10:51 AM k6whp < k6whp@...> wrote: Thought I'd throw this out for the group. I got trapped [sorry!] into schooling some "Baofeng Techs" (FNGs) who are interested in getting into HF about building trap antennas. Of course, being new, they do not have the luxuriant array of test equipment we seem to stack up over the years so I wanted to suggest to them ways they could construct traps and prove out the resulting resonant frequencies of same.
They will be pointed to the appropriate theory, formulas, and internet calculators to derive the component values, inductance, number of turns, etc. but after they have built the traps, I wanted to provide them with a crude but decent method of determining the resonant frequency. (It would not do, after all, to have them wind a 20m trap resonant at 16 MHz.)?
Assume they have a brand new transceiver, can afford a decent VSWR meter, and can lay their hands on stuff like #47 panel lights, LEDs, wire, coax, etc. and know how to solder. They know ought of antenna analyzers, don't have a clue what a GDO is, and other "desert island" stuff like that.
Appreciate any ideas.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
-- Ryan Flowers W7RLF
https://miscdotgeek.com
|
Measuring Resonant Frequency of Traps
Thought I'd throw this out for the group. I got trapped [sorry!] into schooling some "Baofeng Techs" (FNGs) who are interested in getting into HF about building trap antennas. Of course, being new, they do not have the luxuriant array of test equipment we seem to stack up over the years so I wanted to suggest to them ways they could construct traps and prove out the resulting resonant frequencies of same.
They will be pointed to the appropriate theory, formulas, and internet calculators to derive the component values, inductance, number of turns, etc. but after they have built the traps, I wanted to provide them with a crude but decent method of determining the resonant frequency. (It would not do, after all, to have them wind a 20m trap resonant at 16 MHz.)?
Assume they have a brand new transceiver, can afford a decent VSWR meter, and can lay their hands on stuff like #47 panel lights, LEDs, wire, coax, etc. and know how to solder. They know ought of antenna analyzers, don't have a clue what a GDO is, and other "desert island" stuff like that.
Appreciate any ideas.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
If the load is of high enough impedance, you might get by without the push-pull pair.
So I might try first without Q72,Q73, drive your tube rig over a twisted wire pair (or coax)
from the junction between Q71-collector and R75.?
Remember that we had earlier shorted across those two diodes.
Others are more than welcome to chime in, tell us why that won't work.
At least if this circuit smokes, won't be an expensive loss.
Jerry
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On Wed, Dec 18, 2019 at 10:05 AM, Don Richards wrote:
Jerry
I like the idea of the ubitx audio stage. I should have all the parts on hand to give that a try.?
Thanks!
73 Don ve3ids
|
Jerry I like the idea of the ubitx audio stage. I should have all the parts on hand to give that a try.? Thanks! 73 Don ve3ids
On Wed., Dec. 18, 2019, 12:13 p.m. Jerry Gaffke via Groups.Io, <jgaffke= [email protected]> wrote: It is sobering to think how they got by with such simple gear in say, the late 1920's.
Amazing that a single tube regenerative receiver works at all, let alone well enough to use on the ham bands.
A lot of those ham's used that single tube for transmitting also, a few of them on purpose.
A modern DSP rig could have a billion transistors.
Using a perfectly good QRP rig to go from 3v pk-pk to a 10 volt signal would strike them as preposterous.
If Don wants to tinker, a good starting point might be the uBitx v4 push-pull audio amp:
? ??
Start with everything between VOL-M, and SPK, remove C78, short out R71, change caps C72, C73, C74 to 0.1uF,?
We don't need this to be linear, so remove D15 and D16, short across R76 and R77.
(When I say short across", I mean replace that part with a wire.)?
From there it might just work, or could take a few minutes (or months) of learning why it doesn't work.
I have no idea what kind of load Don is actually driving.
The 2n2222a and 2n2907a would be a beefier choice for the transistors.
Jim would approve.
That circuit didn't work very well as an audio amp in the uBitx, v5 went to an LM386.
Here's some food for thought regarding a good simple audio amp, second schematic down:??
? ??
Similar to the uBitx audio amp, except uses an IC as a driver.
That IC would be too slow for use at radio frequencies.
Jerry, KE7ER
On Wed, Dec 18, 2019 at 08:06 AM, Eric KE6US wrote:
It would work fine. I used my K2 as a VFO for a Drake 2NT until I could get something built for it.
We might overthink things in the digital age. They used to be a lot simpler, and the still could be.
Eric kE6US
|
I like the notion of two 74ACT04 gates in push pull.
But wonder what kind of trouble you could get into using that to drive a transformer.
Whenever I see a full description of the design process for a circuit with magnetics,
it seems I always learn something new.?
To use inverters in push-pull, the logical thing would be to invert the original signal with one gate,
then feed the original and the inverted signal into two other inverter gates.
However, prop delay through one gate is spec'd to be somewhere between 1 and 9 ns.
A better choice might be 74ACT86 ex-or gates both driven from the same signal,
the second input held high on one gate and shorted to ground on the other.
Supply sequencing can definitely cause trouble.
Some parts are designed to survive indefinitely, regardless of supply sequencing.
Many parts will live through a millisecond or so of poorly thought out sequencing.
At work, we often had digital designs with a half dozen different supplies.
A single FPGA might have that many.
It was something to worry about, but we generally had plenty of other problems to solve that were more pressing.
Jerry, KE7ER
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On Wed, Dec 18, 2019 at 04:55 AM, Steven Dick wrote:
Something to keep in mind in circuits that use multiple power supplies is power sequencing:? It is important that the 5V comes on before the 3.3V and turns off after the 3.3V when the 3.3V turns off.? Otherwise you can drive the 5V unpowered device from the 3.3V driving chip.? If the 3.3V driving chip can supply a hefty amount of current, you can? possibly damage the input circuitry of the 5V powered device by forward biasing its protection diode if it has one.? That protection diode may see more current than it is designed to handle. Depending on the particular 5V device, it may not immediately fail but can ultimately fail with repeated power sequencing at turn on or turn off.? A possible safety measure is to put a small Schottky diode between the +5V and +3.3V rails in the direction such that the 3.3V supply pulls up the 5V rail if unpowered, until the 5V supply kicks in and turns off that diode.? If the 3.3V supply is derived from the 5V supply, that is normally not a problem. But if the 5V and 3.3V supplies are totally independent, that problem can easily happen. The input clamp current for the 74ACT family has a clamp diode which is pretty hefty (current rating of 20mA) so it¡¯s probably not a problem for the 74ACT chip, but you are momentarily shorting the output of the SI5351 at power up if there is a power sequence problem.
I haven¡¯t tried it myself but if you need a larger voltage than that provided by a single +5V buffer or paralleled buffers, you can wire up the 74ACT04N? to generate a true and complement output.? A.C. couple them to a 1:1 RF transformer to get double the output or 10 volts peak to peak.? If you need more than 10 volts and are driving a high impedance load, then increase the turns ratio to 2 to 1 which will provide 20 volts peak to peak.? You can make your own one to one transformer with a low cost toroid and bifilar winding. Drive one winding with the true and complement outputs. The other winding is the secondary going to the load. You can use trifilar winding for two to 1 turns ratio. Drive one winding with the true and complement outputs.? Put the other two windings in series aiding for the secondary.?? Winding them bifilar or trifilar improves the bandwidth.
|
It is sobering to think how they got by with such simple gear in say, the late 1920's.
Amazing that a single tube regenerative receiver works at all, let alone well enough to use on the ham bands.
A lot of those ham's used that single tube for transmitting also, a few of them on purpose.
A modern DSP rig could have a billion transistors.
Using a perfectly good QRP rig to go from 3v pk-pk to a 10 volt signal would strike them as preposterous.
If Don wants to tinker, a good starting point might be the uBitx v4 push-pull audio amp:
? ??
Start with everything between VOL-M, and SPK, remove C78, short out R71, change caps C72, C73, C74 to 0.1uF,?
We don't need this to be linear, so remove D15 and D16, short across R76 and R77.
(When I say short across", I mean replace that part with a wire.)?
From there it might just work, or could take a few minutes (or months) of learning why it doesn't work.
I have no idea what kind of load Don is actually driving.
The 2n2222a and 2n2907a would be a beefier choice for the transistors.
Jim would approve.
That circuit didn't work very well as an audio amp in the uBitx, v5 went to an LM386.
Here's some food for thought regarding a good simple audio amp, second schematic down:??
? ??
Similar to the uBitx audio amp, except uses an IC as a driver.
That IC would be too slow for use at radio frequencies.
Jerry, KE7ER
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On Wed, Dec 18, 2019 at 08:06 AM, Eric KE6US wrote:
It would work fine. I used my K2 as a VFO for a Drake 2NT until I could get something built for it.
We might overthink things in the digital age. They used to be a lot simpler, and the still could be.
Eric kE6US
|
It would work fine. I used my K2 as a VFO for a Drake 2NT until I
could get something built for it.
We might overthink things in the digital age. They used to be a
lot simpler, and the still could be.
Eric kE6US
On 12/17/2019 7:42 PM, Jerry Gaffke via
Groups.Io wrote:
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Do you have QRP
transmitter lying about capable of at least 2 Watts?
Drive that QRP transmitter with the Si5351,
put a 50 ohm dummy load on the QRP transmitter so you don't blow
it up,
and run coax from that dummy load into your vacuum tube
transmitter.
A two watt transmitter into 50 ohms is? squareroot(2*50) = 10
volts RMS?
If it's more than two watts, you could bring it down by a special
resistive divider dummy load.
Might work.
Jerry
On Tue, Dec 17, 2019 at 06:28 PM, Don Richards wrote:
Jerry
Thanks for the info. I need about 10 volts. What are your
thoughts on this?
?
?
73 Don ve3ids
|
k6whp
Bo, OZ2M
Don VE3IDS