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
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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
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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
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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
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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
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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
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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
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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.
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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.
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Re: 7 MHz Oscillator Ideas
The HiPerMite has no volume control:
? ??
And this radio has no AGC.
So AA7EE's 1k pot is also your only volume control.
Jerry
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On Sat, Dec 7, 2019 at 12:59 PM, Jerry Gaffke wrote:
The 1k pot is for RF gain in case you are dealing with very strong in-band signal,
the SA612 doesn't have a whole lot of dynamic range.
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Re: 7 MHz Oscillator Ideas
That AA7EE front end is fairly straightforward.
The 1k pot is for RF gain in case you are dealing with very strong in-band signal,
the SA612 doesn't have a whole lot of dynamic range.
The tuned bandpass filter that follows the pot prevents strong out-of-band signals
from swamping the SA612, perhaps that 50kW AM broadcast station on the other side of town.
It also prevents harmonics of the desired frequency from sneaking through to the audio.
From the pot, the signal goes into an impedance matching transformer,
the output winding of the transformer is parallel tuned with 50p+47p
That first parallel tuned circuit is lightly coupled via 10p into a second very similar parallel tuned circuit,
the light coupling prevents the two of them from acting as one big tuned circuit at one quarter the resonant frequency.
The 10p also provides DC isolation, note that pin 2 of the SA612 does not want to be at DC ground.
He calls out a NE602, any genuine part marked "NE" would have to be pretty old.
These days NXP makes it, and calls it the SA612.
NXP will also sell you an SA602 if you insist, but it's exactly the same part.
There have also been "new and improved" A variants.
But I don't believe there has been a significant difference between any of these parts for several decades.
The diode tuning should be plenty stable for tuning across a few khz of 40m CW.
Add a cap in parallel with the coil till you hit the desired frequency,
adjust the 1000p cap till you have the desired 15khz range,
If not stable enough, unhook the diode, see if it remains unstable.
If not, then the neighboring caps and/or coil are the problem.
If the diode proves too unstable, make sure your "8vReg" is properly regulated.
NPO caps are very cheap and stable.
Random caps from your junkbox will give random results.
Jerry?
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On Sat, Dec 7, 2019 at 08:47 AM, JT Croteau wrote:
I've been thinking of taking AA7EE's approach at using NM0S's
HiPerMite as the audio chain. I don't fully understand his use of a
tuned BPF, my lack of experience is showing here.
AA7EE Rugster:
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Re: 7 MHz Oscillator Ideas
I've been thinking of taking AA7EE's approach at using NM0S's
HiPerMite as the audio chain. I don't fully understand his use of a
tuned BPF, my lack of experience is showing here.
AA7EE Rugster:
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On Sat, Dec 7, 2019 at 10:10 AM W0PWE <j.b.hall@...> wrote:
I like the receiver section of the SST xcvr for an application like this. It even has a simple AGC that works pretty well. You will probably need another stage of audio amplification if you want to use a speaker rather than headphones.
I deviated from the SST design a little and used the internal oscillator in the NE612 for the vfo. With two crystals in parallel (aka super VXO) and a whole lot of experimentation with various inductors I got a tuning range of better than 25KHz. The 40m design uses 4MHz crystals in the IF and 11.046MHz in the VFO. It has been many years but seems like I used 11.059MHz crystals in mine.
Another good option would be the Universal Receiver Kit from Kits and Parts.
73 - Jerry - W0PWE
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Re: 7 MHz Oscillator Ideas
I used a 7.16 mHz ceramic resonator with great
success.
I had those resonators left over from the VK3YE regen projects.
On 12/07/2019 10:10 AM, JT Croteau
wrote:
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Show quoted text
Hi folks, I'd like to build a simple NE612/LM386 receiver to cover
from roughly 7.028 to 7.042. I'm wondering what I should use for the
oscillator. I've been poking around on google but it is making my
head spin. Minimal drift would be ideal as I'd like to park it on
7040 or 7030 for a few hours just to monitor.
Times like this I wish I still had some of my Doug Demaw books.
Thanks
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Re: 7 MHz Oscillator Ideas - good enough
JT,
This is exactly how I used my old Ramsey kit back in the early '90s.? Had it next to my bed.
It was the same NE602/LM386 design.
An LC osc using the NE602 internal should work fine.
A varicap (actually any diode should give your desired range) is nice and mechanically stable.
The Ramsey kit made the mistake of not voltage regulating the varicap, using a 9V battery,
there was a continuous small drift due to battery voltage drop.
If you use a variable C or L instead of the varicap, the NE602 has internal voltage regulation,
or use a stable supply, not a 9V battery.
GL and 73,
Gary
WB6OGD
toggle quoted message
Show quoted text
On 12/7/2019 7:44 AM, JT Croteau wrote: Hi Bill,
CW only. I just want something to monitor 7030 and 7040 while I am
smoking a pipe and reading in my single room cabin or drifting off to
sleep.
73
On Sat, Dec 7, 2019 at 9:42 AM Bill Cromwell <wrcromwell@...> wrote:
Hi JT,
What modes do you have in mind? CW and most of the digital modes are not
particularly fussy about a little drift. A free running, L-C VFO should
give you what you *need*. The ones I have that use vacuum tubes take a
little longer - up to a half hour to settle down. A couple of the solid
state oscillators settle in a few seconds. For some people, splitting
hairs multiple times is a hobby. Hobbies have their own rewards. Most
amateur modes do not require milliHertz precision.
If you expect to work some of the super slow, deep noise modes like some
of the JT stuff you better look at some of the digital VFO designs and
even some of those are not "good enough".
In my working life we made measurements with resolution and accuracy of
a few millionths of one inch - in some cases two millionths. In my
woodworking hobby that is just ridiculous:) I do hold "some" tolerances
quite a bit closer than the guy who cuts pieces at Home Depot but nobody
gets bragging rights for that:) At home depot the tolerances on those
saws is "good enough". 'Good enough' does not mean "sloppy" or "inferior".
Good luck with your fun project. Merry Christmas and...
73,
Bill KU8H
On 12/7/19 10:10 AM, JT Croteau wrote:
Hi folks, I'd like to build a simple NE612/LM386 receiver to cover
from roughly 7.028 to 7.042. I'm wondering what I should use for the
oscillator. I've been poking around on google but it is making my
head spin. Minimal drift would be ideal as I'd like to park it on
7040 or 7030 for a few hours just to monitor.
Times like this I wish I still had some of my Doug Demaw books.
Thanks
--
bark less - wag more
|
Re: 7 MHz Oscillator Ideas
I like the receiver section of the SST xcvr for an application like this. It even has a simple AGC that works pretty well. You will probably need another stage of audio amplification if you want to use a speaker rather than headphones.
I deviated from the SST design a little and used the internal oscillator in the NE612 for the vfo. With two crystals in parallel (aka super VXO) and a whole lot of experimentation with various inductors I got a tuning range of better than 25KHz. The 40m design uses 4MHz crystals in the IF and 11.046MHz in the VFO. It has been many years but seems like I used 11.059MHz crystals in mine.
Another good option would be the Universal Receiver Kit from Kits and Parts.?
73 - Jerry - W0PWE
|
Re: K1SWL has done it again, the Phaser!
Dave has posted on the CWTD Group his thoughts on using a DC Receiver with the Phaser Transceiver:
"We considered interoperability between Phaser users to be an important design goal.?? That drove the design to single-sideband transmit, and we recently validated that goal with a Phaser-to-Phaser contact.? ? The use of DSB rather than SSB on receive was a simplification and a considerable one at that.? In view of the few instances where we felt this issue would arise, we elected to go forward with 'less complex' and still economical."
?
73- Dave Benson, K1SWL
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Re: 7 MHz Oscillator Ideas - good enough
Hi Bill,
CW only. I just want something to monitor 7030 and 7040 while I am
smoking a pipe and reading in my single room cabin or drifting off to
sleep.
73
toggle quoted message
Show quoted text
On Sat, Dec 7, 2019 at 9:42 AM Bill Cromwell <wrcromwell@...> wrote:
Hi JT,
What modes do you have in mind? CW and most of the digital modes are not
particularly fussy about a little drift. A free running, L-C VFO should
give you what you *need*. The ones I have that use vacuum tubes take a
little longer - up to a half hour to settle down. A couple of the solid
state oscillators settle in a few seconds. For some people, splitting
hairs multiple times is a hobby. Hobbies have their own rewards. Most
amateur modes do not require milliHertz precision.
If you expect to work some of the super slow, deep noise modes like some
of the JT stuff you better look at some of the digital VFO designs and
even some of those are not "good enough".
In my working life we made measurements with resolution and accuracy of
a few millionths of one inch - in some cases two millionths. In my
woodworking hobby that is just ridiculous:) I do hold "some" tolerances
quite a bit closer than the guy who cuts pieces at Home Depot but nobody
gets bragging rights for that:) At home depot the tolerances on those
saws is "good enough". 'Good enough' does not mean "sloppy" or "inferior".
Good luck with your fun project. Merry Christmas and...
73,
Bill KU8H
On 12/7/19 10:10 AM, JT Croteau wrote:
Hi folks, I'd like to build a simple NE612/LM386 receiver to cover
from roughly 7.028 to 7.042. I'm wondering what I should use for the
oscillator. I've been poking around on google but it is making my
head spin. Minimal drift would be ideal as I'd like to park it on
7040 or 7030 for a few hours just to monitor.
Times like this I wish I still had some of my Doug Demaw books.
Thanks
--
bark less - wag more
|
Re: 7 MHz Oscillator Ideas - good enough
Hi JT,
What modes do you have in mind? CW and most of the digital modes are not particularly fussy about a little drift. A free running, L-C VFO should give you what you *need*. The ones I have that use vacuum tubes take a little longer - up to a half hour to settle down. A couple of the solid state oscillators settle in a few seconds. For some people, splitting hairs multiple times is a hobby. Hobbies have their own rewards. Most amateur modes do not require milliHertz precision.
If you expect to work some of the super slow, deep noise modes like some of the JT stuff you better look at some of the digital VFO designs and even some of those are not "good enough".
In my working life we made measurements with resolution and accuracy of a few millionths of one inch - in some cases two millionths. In my woodworking hobby that is just ridiculous:) I do hold "some" tolerances quite a bit closer than the guy who cuts pieces at Home Depot but nobody gets bragging rights for that:) At home depot the tolerances on those saws is "good enough". 'Good enough' does not mean "sloppy" or "inferior".
Good luck with your fun project. Merry Christmas and...
73,
Bill KU8H
toggle quoted message
Show quoted text
On 12/7/19 10:10 AM, JT Croteau wrote: Hi folks, I'd like to build a simple NE612/LM386 receiver to cover
from roughly 7.028 to 7.042. I'm wondering what I should use for the
oscillator. I've been poking around on google but it is making my
head spin. Minimal drift would be ideal as I'd like to park it on
7040 or 7030 for a few hours just to monitor.
Times like this I wish I still had some of my Doug Demaw books.
Thanks
--
bark less - wag more
|
Hi folks, I'd like to build a simple NE612/LM386 receiver to cover
from roughly 7.028 to 7.042. I'm wondering what I should use for the
oscillator. I've been poking around on google but it is making my
head spin. Minimal drift would be ideal as I'd like to park it on
7040 or 7030 for a few hours just to monitor.
Times like this I wish I still had some of my Doug Demaw books.
Thanks
|
Using Re-Purposing those Flat Mobile Phone Cells
From old mobile phones, I've saved several sizes of various AHr capacity cells.
If you don't have a way to make compression contact to the terminals on the top, you can solder to them.
The terminals are not connected directly to the cell, they use spot-welded metal strips** to make the connections. The tiny spot welds don't quickly transfer heat from the terminals on top to the cells underneath the plastic top piece.
For charging without a cell phone, I use one of the universal chargers. Specifically the one with the charge indicator on one end. This one has spring-loaded pushpins that will make contact to rough uneven surfaces like solder connections.eBay has several versions, The least expensive works fine and they will handle a wide-range of cell widths.
<https://www.ebay.com/itm/Mobile-Universal-Battery-Charger-LCD-Indicator-Screen-For-Cell-Phones-1-USB-Port/112928050208?_trkparms=aid%3D1110001%26algo%3DSPLICE.SIM%26ao%3D1%26asc%3D20131231084308%26meid%3D91b72536d82e43799d94256405b46820%26pid%3D100010%26rk%3D3%26rkt%3D12%26mehot%3Dpp%26sd%3D121883657151%26itm%3D112928050208%26pmt%3D0%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100010.m2109>
I'm using one of the re-purposed cells in my SMT keyer and after a couple of years now the voltage is still close to the charge nominal 4.2 V.
** I've taken them apart for a look-see.
--
Chuck, W5USJ (ex K2OFN)
Point, Rains Co, TX? EM22cv
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Re: K1SWL has done it again, the Phaser!
Very similar to the PSKs. When I first worked
JT65, I considered converting my PSK-20 to JT65. In the end, I
couldn't bear to cut up such neat little rig.
I'm glad I didn't. JT modes remind me of stamp
collecting only not as personal. They had one thing going for
them, though. JT65 and JT9 are the only modes I've ever used
where I actually worked the guy who invented them. I'm old, but
Morse and Vail were long gone before I was born.
Eric KE6US
On 12/6/2019 9:42 AM, JT Croteau wrote:
toggle quoted message
Show quoted text
Just like the Warbler and PSK series of days long ago, K1SWL has done
it again by teaming up with N2APB to produce a phasing SSB QRP
transceiver for FT8 and other digital modes. With two frequencies
available and a cost of only $50 per band, we can put our DSB toys out
to pasture.
Kits start shipping Dec. 16th:
I've ordered two thus far.
N1ESE
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Chuck Carpenter
bleepingbeep