Re: What level math is in the RF design books?
I am a 60 year old retired computer programmer......... with
failing vision.
I have written software for everything from tiny microcontrollers
to track satellites with DOS computers to IBM mainframes the size
of a football field.
I have written accounting software and manufacturing software and
911 systems and software for pacemakers in your chest.
and
all ..without ever spending a day in a college classroom.
and
not once....
not ever...?? did a boss ever say to me "solve for X".
In all of that lifetime of computer programming there never was
an algebra exam.
So... now... in my old age and tinkering with radio circuits I
dabble with these books
and
yes...?? Experimental Methods in RF Design is one of them here.
and
I know I don't know anything more than basic algebra.... so when
something like the EBERS-MOLL equation
is presented to me I asked the question ...what math class
teaches how to solve this equation.
?
On 12/09/2019 02:02 PM, Ryan Flowers
wrote:
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Show quoted text
This reminds me of the question I asked in the old
group regarding an oscilloscope. I wondered if it was possible
to homebrew?a sideband transmitter without one, and the answer
was "definitely!" It turns out that even the experienced folks
tune with not much else than another transceiver. Oh, ok! Sounds
good to me lol.?
I think the overall attitude in the homebrew world
gravitates to "learn by doing" no "learn by learning" and I'm
cool with that.?
On the other hand, if I've misunderstood misrepresented
something in that statement, please accept my apologies and
feel free to tell me to shaddup :p?
?
You
will find that there are online calculators or models you
can use for most everything you?might want to do.? The
tougher issue is to understand the how and why of
electronics.? On your own, that will take many years to
learn.? Most of the folks in this group are experts in
their own areas, but will willingly tell you they are
still learning.? So, don't worry about the math or the
hairy technological details, just jump in and enjoy.? Dale
On Mon, Dec 9, 2019 at
8:55 AM Jerry Gaffke via Groups.Io <jgaffke= [email protected]>
wrote:
It all depends on how
deep you want to go.
For example, most radio amateurs would evaluate an antenna
system by measuring the SWR.
But you won't really understand it unless you embrace the
notion of a complex impedance,
and make use of those dim memories of sqrt(-1) from your
high school algebra class.?
Experimental Methods in RF Design (EMRFD) is probably the
book you want.
Anything that fails to go that deep, you will have a hard
time cooking up
new designs that actually work well.? Mostly patching
together pieces of stuff
that other people have published.
You will need a whole lot of time, as it's a thick read
with lots of new concepts.
Some of those pages will take a day of fiddling with
before it really sinks in.
And maybe access to a forum somewhere to ask the
inevitable questions.
It's got plenty of math in there, relative to the typical
QST article.
But nothing I didn't see in a high school algebra class.
I almost never did use calculus in my 40 yr career as an
EE.
Some engineers wind up in a job where they use it every
day.
Figuring out calculus does give you a tool for better
understanding the world,
especially the world of electronics.?
For example, how a capacitor charges up over time.
So useful even if you don't actually *use* it.
Introduction to Radio Frequency design (by the same
author) is a good taste
of what you will run into if you decide to get a degree in
Electrical Engineering.
What you do coming out of school with an EE degree is wide
open.
Could be working on a better generator for Bonneville Dam.
Could be digital design with boards full of FPGA's and
mostly writing VHDL.
Analog design (perhaps a radio), mostly reading ap notes
from chip manufacturers
on their hot new parts, trying out your design in a
simulator on a computer.
Could be getting the recipe just right for a silicon fab
line.
That last one would require intimate knowledge of the
Ebers-Moll model.
For the second to the last, reading EMRFD thoroughly would
get you most of the way there.
Jerry, KE7ER
On Mon, Dec 9, 2019 at 05:40 AM, Michael Maiorana wrote:
Rob,
Start
with college-level algebra. My professor called
algebra "the language of mathematics".?
Then,
Calculus (1, 2 and 3) along with engineering level
Physics (physics with calculus).?
Then
Differential equations.
Then
semiconductor physics and electronic materials.
Then
you'll be there.
?
Or...
you could use the empirical?methods which are covered
thoroughly?in Wes's EMRFD book.
?
Mike M
KU4QO
--
--
Ryan Flowers W7RLF
|
Re: What level math is in the RF design books?
Rob,
Ouch! That's going to leave a mark!
It's a fair cop, as the Brit villains say. I went through college begging for a grade in calculus, retired two years ago and *finally* started to do some of the math I haven't used in 45 years -- even got an HP calculator and learned RPN.
Still have trouble calculating power from Vp-p, however.??
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."
|
Re: What level math is in the RF design books?
And while I'm at it, I'll recommend two other books:
The Art of Electronics, Horowitz and Hill. A classic
RF Circuit Design, Chris Boswick. Lots of practical design info and exercises
Eric KE6US
toggle quoted message
Show quoted text
On 12/9/2019 4:17 AM, Rob via Groups.Io wrote: What level of math course would I need to study to learn how to comprehend the equations presented in
design books like Introduction to Radio Frequency Design?? by W7ZOI.
|
Re: What level math is in the RF design books?
About 15 years ago, I had a website appropriately called
KE6US.com. I actually reviewed both EMRFD and Intro to RF Design.?
Wes was kind enough to send me a thank you email for the reviews.
Experimental Methods in RF Design, by
Wes Hayward (W7ZOI), Rick Campbell (KK7B), Bob Larkin (W7PUA).?
Hands down, the best book on homebrew design for hams ever
published. I refer to it constantly. My copy is dog-eared and
annotated on almost every page. I have modeled a number of the
circuits in SPICE.? I have also built quite a few of them.
Includes a jam-packed CD of valuable articles and other stuff.
Published by?.
Introduction to Radio Frequency Design,
by Wes Hayward (W7ZOI). You best pour through "Introduction to
Advanced Mathematics" and "Introduction to Electronic Design"
before tackling this one. I doubt the average ham would find
this book useful. It was originally published by Prentice-Hall
as a text for the "working engineer". Wes says he wished it
was available for his "career change from electron device
physics to rf circuit design." If you're contemplating a
similar career change, I recommend this book, otherwise, you
might want to hold off. There are lots of books better suited
to even advanced hams. Published by?.
I understand that level of math. In
grad school (economics), I took most math classes with engineering
students. However, understanding the math doesn't necessarily
equip you for understanding the concepts. I am a native English
speaker, but that doesn't mean I can understand everything a
theoretical physicist or classical philosopher has to say...in
English.
So I stand by what I said at the time.
For even above average hams, stick with EMRFD. You will need high
school math at most and a very curious mind. If you can get
through everything in that book, you won't need much else for
empirical design. I wouldn't discourage seriously skimming RFD
though.
Eric KE6US
On 12/9/2019 4:17 AM, Rob via Groups.Io
wrote:
toggle quoted message
Show quoted text
What level of
math course would I need to study to learn how to comprehend the
equations presented in
design books like Introduction to Radio Frequency Design?? by?
W7ZOI.
|
Re: What level math is in the RF design books?
It's one thing to build a known good design.
Quite another to design something that is fundamentally novel,
making the necessary calculations and measurements to get it performing well.
Yes, you can tinker with stuff and iterate to something that works better.
Sometimes.
But you will have much better luck if you understand what's going on.
When designing a radio there are many itradeoffs to be made.
You will need more than another transceiver to fully evaluate some new design.
Jerry, KEy7ER
?
toggle quoted message
Show quoted text
On Mon, Dec 9, 2019 at 11:02 AM, Ryan Flowers wrote:
This reminds me of the question I asked in the old group regarding an oscilloscope. I wondered if it was possible to homebrew?a sideband transmitter without one, and the answer was "definitely!" It turns out that even the experienced folks tune with not much else than another transceiver. Oh, ok! Sounds good to me lol.?
?
I think the overall attitude in the homebrew world gravitates to "learn by doing" no "learn by learning" and I'm cool with that.?
?
On the other hand, if I've misunderstood misrepresented something in that statement, please accept my apologies and feel free to tell me to shaddup :p?
?
|
Re: What level math is in the RF design books?
This reminds me of the question I asked in the old group regarding an oscilloscope. I wondered if it was possible to homebrew?a sideband transmitter without one, and the answer was "definitely!" It turns out that even the experienced folks tune with not much else than another transceiver. Oh, ok! Sounds good to me lol.?
I think the overall attitude in the homebrew world gravitates to "learn by doing" no "learn by learning" and I'm cool with that.?
On the other hand, if I've misunderstood misrepresented something in that statement, please accept my apologies and feel free to tell me to shaddup :p? ?
You will find that there are online calculators or models you can use for most everything you?might want to do.? The tougher issue is to understand the how and why of electronics.? On your own, that will take many years to learn.? Most of the folks in this group are experts in their own areas, but will willingly tell you they are still learning.? So, don't worry about the math or the hairy technological details, just jump in and enjoy.? Dale
On Mon, Dec 9, 2019 at 8:55 AM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: It all depends on how deep you want to go.
For example, most radio amateurs would evaluate an antenna system by measuring the SWR.
But you won't really understand it unless you embrace the notion of a complex impedance,
and make use of those dim memories of sqrt(-1) from your high school algebra class.?
Experimental Methods in RF Design (EMRFD) is probably the book you want.
Anything that fails to go that deep, you will have a hard time cooking up
new designs that actually work well.? Mostly patching together pieces of stuff
that other people have published.
You will need a whole lot of time, as it's a thick read with lots of new concepts.
Some of those pages will take a day of fiddling with before it really sinks in.
And maybe access to a forum somewhere to ask the inevitable questions.
It's got plenty of math in there, relative to the typical QST article.
But nothing I didn't see in a high school algebra class.
I almost never did use calculus in my 40 yr career as an EE.
Some engineers wind up in a job where they use it every day.
Figuring out calculus does give you a tool for better understanding the world,
especially the world of electronics.?
For example, how a capacitor charges up over time.
So useful even if you don't actually *use* it.
Introduction to Radio Frequency design (by the same author) is a good taste
of what you will run into if you decide to get a degree in Electrical Engineering.
What you do coming out of school with an EE degree is wide open.
Could be working on a better generator for Bonneville Dam.
Could be digital design with boards full of FPGA's and mostly writing VHDL.
Analog design (perhaps a radio), mostly reading ap notes from chip manufacturers
on their hot new parts, trying out your design in a simulator on a computer.
Could be getting the recipe just right for a silicon fab line.
That last one would require intimate knowledge of the Ebers-Moll model.
For the second to the last, reading EMRFD thoroughly would get you most of the way there.
Jerry, KE7ER
On Mon, Dec 9, 2019 at 05:40 AM, Michael Maiorana wrote:
Rob,
Start with college-level algebra. My professor called algebra "the language of mathematics".?
Then, Calculus (1, 2 and 3) along with engineering level Physics (physics with calculus).?
Then Differential equations.
Then semiconductor physics and electronic materials.
Then you'll be there.
?
Or... you could use the empirical?methods which are covered thoroughly?in Wes's EMRFD book.
?
Mike M
KU4QO
--
-- Ryan Flowers W7RLF
https://miscdotgeek.com
|
Re: What level math is in the RF design books?
You will find that there are online calculators or models you can use for most everything you?might want to do.? The tougher issue is to understand the how and why of electronics.? On your own, that will take many years to learn.? Most of the folks in this group are experts in their own areas, but will willingly tell you they are still learning.? So, don't worry about the math or the hairy technological details, just jump in and enjoy.? Dale
On Mon, Dec 9, 2019 at 8:55 AM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: It all depends on how deep you want to go.
For example, most radio amateurs would evaluate an antenna system by measuring the SWR.
But you won't really understand it unless you embrace the notion of a complex impedance,
and make use of those dim memories of sqrt(-1) from your high school algebra class.?
Experimental Methods in RF Design (EMRFD) is probably the book you want.
Anything that fails to go that deep, you will have a hard time cooking up
new designs that actually work well.? Mostly patching together pieces of stuff
that other people have published.
You will need a whole lot of time, as it's a thick read with lots of new concepts.
Some of those pages will take a day of fiddling with before it really sinks in.
And maybe access to a forum somewhere to ask the inevitable questions.
It's got plenty of math in there, relative to the typical QST article.
But nothing I didn't see in a high school algebra class.
I almost never did use calculus in my 40 yr career as an EE.
Some engineers wind up in a job where they use it every day.
Figuring out calculus does give you a tool for better understanding the world,
especially the world of electronics.?
For example, how a capacitor charges up over time.
So useful even if you don't actually *use* it.
Introduction to Radio Frequency design (by the same author) is a good taste
of what you will run into if you decide to get a degree in Electrical Engineering.
What you do coming out of school with an EE degree is wide open.
Could be working on a better generator for Bonneville Dam.
Could be digital design with boards full of FPGA's and mostly writing VHDL.
Analog design (perhaps a radio), mostly reading ap notes from chip manufacturers
on their hot new parts, trying out your design in a simulator on a computer.
Could be getting the recipe just right for a silicon fab line.
That last one would require intimate knowledge of the Ebers-Moll model.
For the second to the last, reading EMRFD thoroughly would get you most of the way there.
Jerry, KE7ER
On Mon, Dec 9, 2019 at 05:40 AM, Michael Maiorana wrote:
Rob,
Start with college-level algebra. My professor called algebra "the language of mathematics".?
Then, Calculus (1, 2 and 3) along with engineering level Physics (physics with calculus).?
Then Differential equations.
Then semiconductor physics and electronic materials.
Then you'll be there.
?
Or... you could use the empirical?methods which are covered thoroughly?in Wes's EMRFD book.
?
Mike M
KU4QO
|
Re: 7 MHz Oscillator Ideas
Chuck, that looks pretty good.
How much tuning range do you get?
Is it best to have the crystals of slightly different frequency, and by how much?
How sensitive is the tuning to changes in battery voltage?
The crystals would give stability, but would lock you into tuning just a few khz.
Maybe an option to switch from the crystals to an LC tank circuit,
so the user can explore something other than a few CW signals.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Mon, Dec 9, 2019 at 04:08 AM, Chuck Carpenter wrote:
Kinda late with this.? Attached a schematic and picture?of a simple RX that I've built?like you mentioned.? They are based on versions of the original MRX-40 in 1997 QST, the original Sudden RX from GQRP, Sudden Rx from QRPme and others.?Info available.? The assembled version is from an artwork I did using ExpressPCB.
The front end can be the tunable version shown or a band pass.? I've worked up a couple of BPFs that tested nicely using simple thru-hole parts.
Using crystals as VXOs gives you tuning range and crystal stability.?
|
Re: What level math is in the RF design books?
It all depends on how deep you want to go.
For example, most radio amateurs would evaluate an antenna system by measuring the SWR.
But you won't really understand it unless you embrace the notion of a complex impedance,
and make use of those dim memories of sqrt(-1) from your high school algebra class.?
Experimental Methods in RF Design (EMRFD) is probably the book you want.
Anything that fails to go that deep, you will have a hard time cooking up
new designs that actually work well.? Mostly patching together pieces of stuff
that other people have published.
You will need a whole lot of time, as it's a thick read with lots of new concepts.
Some of those pages will take a day of fiddling with before it really sinks in.
And maybe access to a forum somewhere to ask the inevitable questions.
It's got plenty of math in there, relative to the typical QST article.
But nothing I didn't see in a high school algebra class.
I almost never did use calculus in my 40 yr career as an EE.
Some engineers wind up in a job where they use it every day.
Figuring out calculus does give you a tool for better understanding the world,
especially the world of electronics.?
For example, how a capacitor charges up over time.
So useful even if you don't actually *use* it.
Introduction to Radio Frequency design (by the same author) is a good taste
of what you will run into if you decide to get a degree in Electrical Engineering.
What you do coming out of school with an EE degree is wide open.
Could be working on a better generator for Bonneville Dam.
Could be digital design with boards full of FPGA's and mostly writing VHDL.
Analog design (perhaps a radio), mostly reading ap notes from chip manufacturers
on their hot new parts, trying out your design in a simulator on a computer.
Could be getting the recipe just right for a silicon fab line.
That last one would require intimate knowledge of the Ebers-Moll model.
For the second to the last, reading EMRFD thoroughly would get you most of the way there.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Mon, Dec 9, 2019 at 05:40 AM, Michael Maiorana wrote:
Rob,
Start with college-level algebra. My professor called algebra "the language of mathematics".?
Then, Calculus (1, 2 and 3) along with engineering level Physics (physics with calculus).?
Then Differential equations.
Then semiconductor physics and electronic materials.
Then you'll be there.
?
Or... you could use the empirical?methods which are covered thoroughly?in Wes's EMRFD book.
?
Mike M
KU4QO
|
Re: What level math is in the RF design books?
Rob, Start with college-level algebra. My professor called algebra "the language of mathematics".? Then, Calculus (1, 2 and 3) along with engineering level Physics (physics with calculus).? Then Differential equations. Then semiconductor physics and electronic materials. Then you'll be there.
Or... you could use the empirical?methods which are covered thoroughly?in Wes's EMRFD book.
Mike M KU4QO
What level of math course would I need to study to learn how to comprehend the equations presented in
design books like Introduction to Radio Frequency Design?? by? W7ZOI.
I have been tinkering with circuits from these books for 50 years but never really learned what is in the math.
There are all sorts of online math course now so.....
What level of math class would teach this gobbledygoop?
and
Do any of you? ACTUALLY use this level of math to build radios or is the math only used by
the guys designing the transistors????
73 Rob KB3BYT
|
Re: What level math is in the RF design books?
I agree with Diz on empirical design.? Although I find that collage?algebra** 101?can be most?useful.? Also some high school trig and calculus.? That so when you are reading a paper about some?basic?design, you have an idea what the symbols mean and what they are doing...8^)
Otherwise, there is a lot of good work out there that you can integrate ?into your project. And the more you do the better you get at it.
**At least 8th grade Algebra as I learned it c. 1950s.??Math they are teaching 5th graders now overwhelms me!
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
|
Re: What level math is in the RF design books?
OK...I'll start a fire here...
I believe that empirical RF designs will outperform
mathematically designed RF hardware every time.
Let the flame war begin :)
Seriously, I personally do not go beyond using frequency
determining math to calculate resonance
and transistor bias resistors using ohms law and 0.6? transistor
voltage drops.
Seems I always end up adjusting circuit values after what the
math tells me to do.
YMMV...as usual.
-Diz (no offense to any math geniuses out there...)
On 12/9/19 7:17 AM, Rob via Groups.Io
wrote:
toggle quoted message
Show quoted text
What level of math course would I need to study to learn how to
comprehend the equations presented in
design books like Introduction to Radio Frequency Design?? by?
W7ZOI.
I have been tinkering with circuits from these books for 50 years
but never really learned what is in the math.
There are all sorts of online math course now so.....
What level of math class would teach this gobbledygoop?
and
Do any of you? ACTUALLY use this level of math to build radios or
is the math only used by
the guys designing the transistors????
73 Rob KB3BYT
|
What level math is in the RF design books?
What level of math course would I need to study to learn how to comprehend the equations presented in
design books like Introduction to Radio Frequency Design?? by? W7ZOI.
I have been tinkering with circuits from these books for 50 years but never really learned what is in the math.
There are all sorts of online math course now so.....
What level of math class would teach this gobbledygoop?
and
Do any of you? ACTUALLY use this level of math to build radios or is the math only used by
the guys designing the transistors????
73 Rob KB3BYT
|
Re: 7 MHz Oscillator Ideas
JT,
Kinda late with this.? Attached a schematic and picture?of a simple RX that I've built?like you mentioned.? They are based on versions of the original MRX-40 in 1997 QST, the original Sudden RX from GQRP, Sudden Rx from QRPme and others.?Info available.? The assembled version is from an artwork I did using ExpressPCB.
The front end can be the tunable version shown or a band pass.? I've worked up a couple of BPFs that tested nicely using simple thru-hole parts.
Using crystals as VXOs gives you tuning range and crystal stability.?
----------------------------------------------------
Note that I keep my attachments to about 1/2 Mb or so.
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
|
Re: Plug and Play Receiver
The Rugster from AA7EE we've been discussing here uses the HiPerMite audio filter,?
which is a very good CW filter but I think a beginner's receiver should just let them hear
the whole audio spectrum.? ?Then they can also hear SSB or even AM stations if the thing
is tuned to an appropriate band segment.
W7ZOI's book EMRFD starts out with a nice simple DC receiver in figure 1.9 on page 1.8.
Just an SA612 plus an LM386, plus a minimum of other parts.
This is probably the circuit I would build first, and compare anything else with.
The variable cap might cost a bit more than a 1n4001, but more linear, and less sensitive to supply noise.
AA7EE also posted this other DC receiver for 80m back in 2012, similar to the EMRFD 40m receiver.
And the whole thing is simpler than putting together a HiPerMite.
? ??
Both the EMRFD 40m receiver and the AA7EE 80m receiver have a single tuned input filter.
AA7EE mentions in the Rugster post that he lives in a built up urban area, and so wanted to try a double tuned circuit.
There is also a lot of variation in the local oscillator.
AA7EE's Rugster uses a varactor diode in an LC circuit.
But his 80m DC receiver uses a ceramic resonator plus varactor diode.
The EMRFD design uses a nice traditional variable cap in an LC circuit.
If you are designing "modules" to make building a receiver easier, I guess that's an SA612 and an LM386?
that get plugged together like two lego blocks.? I'm not so sure I see much point in that.
I'd tend to just give them an etched PC board and a sack of parts.
For small hands and sharp eyes, 1206 and SOIC surface mount parts may not be an issue.
Have them put together the audio amp first and get that working, it can be useful all by itself.
Have a scope on hand (a clone DSO138 kit is now $8 on ebay!) so they can see the audio signals.
The SA612 section could be a bit more tricky to get working correctly,
make sure you have that fully figured out before turning it loose on a bunch of kids.??
Include a good write up, Dave Benson's SW40+ manual is a great example of good.
Note that the SA612 local oscillator for a DC receiver is at the receive frequency.
So you could let the kids play with sending morse code across the room by keying that oscillator.
And if there's more than a couple kids in the group, they will learn what QRM is.
If you really want a CW filter on this DC receiver but think the HiPerMite is a bit too complicated,
then steal the filter and audio amp from the SW40+.??? ?
? ? ?
You probably don't need the FET switch though,?it is there to mute the receiver during transmit.??
So remove it, and short across where Source and Drain were.
Otherwise, just follow his lead on everything from the SA612 audio output pins to the headphones.
The op amp he uses probably won't drive a speaker, but at least in my household
nobody else wants to hear a lot of CW.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Sun, Dec 8, 2019 at 06:34 PM, n3fel@... wrote:
Jerry, Just a coincidence but I've also been searching for an interesting project for young builders to tinker with radio circuits.? AA7EE's receiver sketch might serve the purpose.? Would there be any interest in this group to move this design to plug and play modules that when implemented would result in a functioning 40m receiver?? The target audience would be kids in the 8-13 yr range.?? Best to center the operating frequency on ARRL's W1AW broadcasts at 7.0475 MHz.? If not this radio, any suggestions?? Must be cheap and reproducible.? By the way, have a browse through the local dollar store where you will occasionally find really affordable electronic stuff.? I recently snagged a few of their powered speaker modules that could easily amplify the HiPerMite headphone output to comfortable desk-top audio.? Howard, n3fel
|
Jerry, Just a coincidence but I've also been searching for an interesting project for young builders to tinker with radio circuits.? AA7EE's receiver sketch might serve the purpose.? Would there be any interest in this group to move this design to plug and play modules that when implemented would result in a functioning 40m receiver?? The target audience would be kids in the 8-13 yr range.?? Best to center the operating frequency on ARRL's W1AW broadcasts at 7.0475 MHz.? If not this radio, any suggestions?? Must be cheap and reproducible.? By the way, have a browse through the local dollar store where you will occasionally find really affordable electronic stuff.? I recently snagged a few of their powered speaker modules that could easily amplify the HiPerMite headphone output to comfortable desk-top audio.? Howard, n3fel
|
Re: Norcal 40a (Was Re: [qrptech] Group Introduction: If you're going to post on the group, reply here!)
Using the 40A for WES today, set at 1W output and it is still a lot of fun. So far QSOs to IN and OH.?
Did anyone ever successfully extend the tuning range of this project to take in more of the band?? Mine tunes from 7020-7062, would be nice to also take in the old Novice section of the band, lot of folks frequent 7100-7125.? I was thinking maybe somehow using a switch to change capacitance in the VFO a little to provide two segments of the band.? I don't want to tear up the radio, but a switch and a capacitor shouldn't add too much complexity.
Curt KB5JO
|
Re: 7 MHz Oscillator Ideas
Just FYI:
From the assembly manual, p.2:? "A user wanting a volume control may substitute a 100k audio
potentiometer for R11 and R12."
Jerry AA6KI
|
Re: 7 MHz Oscillator Ideas
Thanks Jerry, that helps quite a bit. I may change out t a different BPF design as I have no strong signals of any kind near me. I live out in the middle of the woods and don't have any neighbors. On Sat, Dec 7, 2019 at 4:48 PM Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Correction:
the light coupling prevents the two of them from acting as one big tuned circuit at one quarter the resonant frequency. freq = 1/(2*pi*sqrt(L*C))
So doubling both L and C with cut the frequency in half.
Not to a quarter of the original frequency.
|
Re: 7 MHz Oscillator Ideas
Correction:
> the light coupling prevents the two of them from acting as one big tuned circuit at one quarter the resonant frequency.
freq = 1/(2*pi*sqrt(L*C))
So doubling both L and C with cut the frequency in half.
Not to a quarter of the original frequency.
|
k6whp
Dale Hardin KS4NS
Chuck Carpenter
bleepingbeep