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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."
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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
|
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."
|
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
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Might not be a good idea to test the traps in isolation.
The remainder of the antenna system can affect resonance.
|
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.
|
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.
|
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."
|
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.
|
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:
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."
|
whats the FNG mean?
On 12/18/2019 04:12 PM, Eric KE6US
wrote:
toggle quoted message
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.
|
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."
|
Don't forget the "noise bridge".? Here is a simple one that can be built out of junk parts:
It is a very useful and cheaply built antenna testing tool.? Dale KS4NS
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I second what Dale says, however (since measuring traps is the subject),? a simple noise generator along with a receiver can be employed to measure traps.? Example:???>.
73.......Steve Smith WB6TNL
? ? ? ? ? ? ? ? "Snort Rosin"
?On Thu, Dec 19, 2019 at 02:07 PM, Dale Hardin wrote:
toggle quoted message
Show quoted text
Don't forget the "noise bridge".? Here is a simple one that can be built out of junk parts:
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This little noise generator would work fine: ??
On Thu, Dec 19, 2019 at 4:26 PM sigcom1 < sigcom@...> wrote: I second what Dale says, however (since measuring traps is the subject),? a simple noise generator along with a receiver can be employed to measure traps.? Example:???>.
73.......Steve Smith WB6TNL
? ? ? ? ? ? ? ? "Snort Rosin"
?On Thu, Dec 19, 2019 at 02:07 PM, Dale Hardin wrote:
Don't forget the "noise bridge".? Here is a simple one that can be built out of junk parts:
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Gents,
Absolutely great!
Thanks for these suggestions and links! If this does not drag them out of Baofeng "Tech-hood" nothing will.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
k6whp
Dale Hardin KS4NS