Re: Benchtop DMM Recommendation
Wow. Didn't know these devices existed. Nifty!
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
On Monday, May 5, 2025 at 12:45:29 PM CDT, Barb WB2CBA via groups.io <wb2cba@...> wrote:
I am using this. It¡¯s a 3 in 1 device, scope, dvm and signal generator. For the price it is plenty.
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73
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Barb WB2CBA
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Re: Benchtop DMM Recommendation
I am using this. It¡¯s a 3 in 1 device, scope, dvm and signal generator. For the price it is plenty.
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73
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Barb WB2CBA
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Re: Which frequency governs the Si5351 initial phase offset calculation?
Let's try to analyze the clock path to find the answer.
Assuming 2 outputs (CLK0 and CLK1) use the same VCO. The first block after the VCO (not really, but this makes the analysis easier) is the phase offset delay, from 0 to 127 quarter VCO periods set by CLKx_PHOFF[6:0]. This is explained in AN-619, ch.6 (which has a typo stating that CLKx_PHOFF is 5-bit wide, not 7-bit wide as in the register map).
Then there is the Multisync fractional divider, then there is the output (2**R) divider. Dividers reduce the phase offset proportionally. For example, if CLKx_PHOFF=4 and the divider is 4, then the output offset is 90 degrees.
We will use phase offset 0 in CLK0 path. In CLK1 path, the phase difference in degrees is 90 (remember, VCO quarter period) times CLK1_PHOFF, divide by the combined MSD and R ratio.
Now you can see that 90 degrees on the CLK1 output can be achieved only if the output frequency is greater than 600MHz/126 = 4.76MHz. If you set the combined MSD*(2**R) to more than 126 and attempt to set a lower output F, the phase offset can only be less than 90 degrees, because the max phase offset added by CLK1_PHOFF is not enough.
This limit holds whether you use MSD or R, it is the combined divider ratio that counts.
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There is a trick described by Uebo-san here (use Google translate):
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In short, if you start with phase offset of 0 then offset the frequency by a known amount for a known time (then 2 frequencies are equal again), you will get an arbitrary phase offset for arbitrary frequency. The problem is to control the time precisely.
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73, Mike AF7KR
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Which frequency governs the Si5351 initial phase offset calculation?
Hello fellow QRP enthusiasts,
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I know this topic has been discussed here before? but I'm still a little confused as to which frequency / timebase is used to compute the value of the initial phase offset register.
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The tutorial on RFzero () gives an example of the calculation based on the integer part of the output multisynth divider (OMD). This implies that it is the output frequency of the output multisynth which determines the phase offset, not the output frequency after the additional output divider R?
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Another way to ask this question is: where is the phase offset added to the signal? Before the R divider or after?
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I've played around with a Python script that directly enumerates all possible register setting choices for a given output frequency and 90 degree phase offset and I seem to be able to get valid values that are well below the 4.762 MHz limit given by? RFzero using? R > 1.
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Thank you!
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73
DL1YE
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On Sat, May 3, 2025 at 02:58 PM, Curt wrote:
In my stash of QRP rigs is an 80m design by Dan Tayloe kitted by the Az Scorpions- not recalling its name but it was a non-cancelling direct conversion transceiver.
It was the Fort Tuthill 80, known also as the Tut80. It's a nice little rig. I modified mine for varactor tuning with a 10-turn pot (suggested by Cam N6GA) and a KD1JV Digital Dial, as well as modding the PA for a little more power, with a mod suggested by Dan. For a while, Pacific Antenna were selling versions for Top Band and 15M. I thought about acquiring one of them, but didn't get round to it before they sold out. I have also thought about looking for another original 80M one and modding it for 40 but you know how these things go - lots of ideas but limited time and energy!
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I have only used it occasionally, but my one big success was using it to QSO with the T32C DXpedition team on Christmas Island, with the Tut80 into a co-ax fed 40M dipole! By all accounts it shouldn't have worked, but it did, and the ops at T32C had great ears.
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Dave
AA7EE
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Kirk?
Wow, you've really done well.? My annual forays on 160 can be counted on one hand.? I'm not much of a contester and I don't chase various awards.....but I've found the Stew Perry event much to my liking.? I'm good for about 6 or 7 hours before I'm exhausted.? I have no idea how some big time contesters maintain such high QSO rates for extended periods of time.
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There's an interesting piece floating around on the internet about W1BB's favorite antennas.? ?It's at:
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I'm quite struck by Stew's high opinion of an inverted-vee with an apex of 50' to 70' with the ends 15 - 20' off the ground.? Typically antennas this low are viewed as cloud-warmers.? Maybe, given his QTH on the densely populated Eastern seaboard, such an antenna would be very fruitful in a contest.? I can think of no other reason.
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73
Jerry W
KI4IO
Warrenton, VA
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@ KI4IO:? Yes, agree 100% that on 160, it's all about the antenna. But I think your particular inverted-L is a bit higher up in the ranks than you might think. In 2017/2018, when the ionosphere was still in "low band" mode and all the high bands were dead, I worked WAS 160 QRP CW in three months of casual contest participation. (DXCC entities total 21 to date on 160.) I ran 5 W to my own inverted-L, which has a meager 40-foot vertical run and the rest horizontal, out to a treetop (107 feet in total).
I have 32x, 45-foot ground radials, and I have an autotuner in an insulated box at the feed point. There's a large relay in there, too, to select between 107-foot and 41-foot wire elements).
Compared to any horizontally polarized antenna I've ever used, this is a KILLER antenna for the low bands. I wish I would have figured this out about 40 years ago. :)? Since I arrived on the bands in 1977, I had worked about 10 DXCC entities on 80 meters and none other than Canada on 160. Since the "vertical era" My 80-meter QRP entity tally is between 50 and 60, with 160 at 21.?
I was really worried about working KH6 on 160 QRP...until I worked 8 in one evening because there was a bona fide OPENING. :) ? That opening also put JA and VK in the QRP log on CW. Thanks to the wire vertical I am now only a handful of states away from 5BWAS QRP. Ironically, only the nearby ring of states on 15 and 10 meters remain... The vertical has been of no help there.
At any rate, for low-band DX, go vertical!?
Horizontal antennas of any type still put QSOs in the logbook locally and regionally, even at QRP, but DX is extremely limited.
Regards,
Kirk, NT0Z Rochester, MN
PS Propagation on the low bands during solar peaks (now-ish) is generally terrible, which is why I'm trying to fill in stuff on the high bands nowadays. I need only AK and HI to make WAS QRP on 6 meters. DO you think I could catch a break with an afternoon of F2? Not so far...
My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
On Saturday, May 3, 2025 at 07:24:42 PM CDT, Gerald Wolczanski via groups.io <jerrywlinux@...> wrote:
The price of admission for 160 is an efficient antenna.? I'm probably at the low end with a 165' inverted-L up 75' with 47 mixed length radials from 15 to 70'.? I use a K2 at 5 Watts.? ?
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I like the Stew Perry event held around the end of the year.? Participation is dropping off and the propagation (good for the higher bands!) is not so good for 160.? I've gone from 194 QSO's in 2020 to 81 this past year.? In 2020, I forgot and started out at 10 Watts, reducing my power to 5 Watts as I got rolling - so to keep a clean conscience I had to put myself in the QRO division.?
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I had 24 QSO's in the recent NAQCC 160 meter sprint.? ?
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I've had to deal with local noise issues, one of which was a nearby sodium street lamp that was trying, and failing, to ignite.??
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I've pretty much avoided the 160 contests/sprints during the warmer months because of the noise levels. YMMV
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73
Jerry W
KI4IO
Warrenton, VA
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Howard,?
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Though the thought of building an "NC160A" would be poo-pooed in some quarters, because I needed an excuse to warm up my iron, I purchased a 160m 1Watter from Diz, and it resulted in a nice little rig. Also, I have built an NC30A and built two "VFO boards". With reference to your build sequence, I would do the VFO first, the XCVR second, the audio next, and the XMTR last.
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The VFO can be done easily with a small subset of parts - the PS, the VFO, and the RIT circuit. (Only requires a few more parts since you are going to build a full rig eventually.)
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Thus, you can play around with the resulting VFO to get a feel for what a wonderfully stable circuit that is. The real challenge is winding that 60-odd? coil but past experience and counseling inclines towards doing 62 turns as it is easier to unwind than wind. Also, you do not need to secure the coil (l9) with the poly screw and nut (yet). Just mount it flush with some 1-2" leads and tack them to the holes with a blob of solder.? Aim for an inductance of 21 uH.
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The real trick is to set the frequency of the VFO is to pad C50 and get it into the calculated frequency for your IF crystal set. If you have the exotic C50 trimmer, good. You can pad it with an additional NP0 cap on the bottom of the board. If you don't, do what Chuck suggests and build up the capacitance with 10-100 pF NP0 caps until the freq starts at the bottom of your desired range. This, of course, must be done with R17 in place. (The VFO board on the right uses the DuPont pins and a 10K variable resistor.)
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Best of luck! Let us know how it turns out.
--
William, k6whp
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"Cheer up, things could get worse. So I cheered up and things got worse."
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VFO SCHEMATIC
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VFO BOARDS
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The price of admission for 160 is an efficient antenna.? I'm probably at the low end with a 165' inverted-L up 75' with 47 mixed length radials from 15 to 70'.? I use a K2 at 5 Watts.? ?
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I like the Stew Perry event held around the end of the year.? Participation is dropping off and the propagation (good for the higher bands!) is not so good for 160.? I've gone from 194 QSO's in 2020 to 81 this past year.? In 2020, I forgot and started out at 10 Watts, reducing my power to 5 Watts as I got rolling - so to keep a clean conscience I had to put myself in the QRO division.?
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I had 24 QSO's in the recent NAQCC 160 meter sprint.? ?
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I've had to deal with local noise issues, one of which was a nearby sodium street lamp that was trying, and failing, to ignite.??
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I've pretty much avoided the 160 contests/sprints during the warmer months because of the noise levels. YMMV
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73
Jerry W
KI4IO
Warrenton, VA
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As AA7FO mentioned this matter, here is what I can share. ?
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On 160m I have had several CW QSOs with folk operating simple tube transmitters at 5 to 10 watts. ?So it¡¯s definitely viable during the cool season. ?Each year QRP ARCI runs a 160m contest and I have enjoyed memorable QSOs with well-known QRP ops. ?Then for a few years I missed it, as it occurs mid week before the ARRL contest. ?I operated some years in that ARRL contest running 5 watts, into an inefficient short vertical (MA160V) at my prior QTH and did okay. ?
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On 80m of course it¡¯s a bit easier. ?In my stash of QRP rigs is an 80m design by Dan Tayloe kitted by the Az Scorpions- not recalling its name but it was a non-cancelling direct conversion transceiver. ?Sitting in my shack just now is a QCX+ operating with its matching PA that operates around 20 watts output (when run at 13.8 volts) - a fun addition but it also does okay barefoot. ?
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I also operated a little WSPR and found when dropping down to 80 and 160 meters my 300 mW signal from a QRP-Labs U3S did not cross oceans as I did on 40 meters and up - but with better antennas at my present QTH I will try again. ?Here I am using an 80m EFHW configured as an inverted V for 80 and 40 meters, and I have a full size 160m inverted L (now that I have trees to host it here). ?
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No tube transmitters or all band receivers made my move, but I have a simple IRF510 transmitter for stalling operation on 80 and 40 meters. ?Oh and a 160m LPF assembled for use with my uBITX. ?
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QRP is viable on the low bands, and of course old-fashioned VFO and PTO work well down here. ?Still we should have opportunities at the upper spectrum for a few more years (I hope) for this cycle. ?
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Curt wb8yyy
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In response to AF7KR's question:
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"Speaking of boards. ?What is going to be the economics now of getting
PCBWay or other boards from China? "
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Here's a link to JLCPCB's FAQ about tariffs:
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The 2 most relevant FAQ's are:
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2.1 What?proportion?does?JLCPCB?use?to?calculate?the?pre-collected?import?fees?
¡ñ The?proportion?used?by?JLCPCB?to?collect?import?fees?is:?175%.
(°Õ³ó±ð?²¹³¾´Ç³Ü²Ô³Ù?¾±²Ô³¦±ô³Ü»å±ð²õ?³Ù³ó±ð?±ð²õ³Ù¾±³¾²¹³Ù±ð»å?³Ù²¹°ù¾±´Ú´Ú?´Ç´Ú?170%,?±è±ô³Ü²õ?´³³¢°ä±Ê°äµþ'²õ?10±«³§¶Ù?³Ù²¹³æ?²¹»å±¹²¹²Ô³¦±ð?´Ú±ð±ð?´Ç°ù?5%?´Ç´Ú?³Ù³ó±ð?³Ù´Ç³Ù²¹±ô?³Ù²¹³æ,?·É³ó¾±³¦³ó±ð±¹±ð°ù?¾±²õ?³ó¾±²µ³ó±ð°ù£©
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2.2 How does JLCPCB address differences between pre-collected and actual taxes?
¡ñ Adjust payments to match actual costs: JLCPCB will ensure that payments are corrected by refunding for overpayments and charging for shortfalls.
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So not only are you going to pay the estimated tariff, you also have to pay a tax advance fee on top of that. Plus, if there are any additional tariffs due, you'll be back billed for them.
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Sounds like this is an untenable situation.
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My strategy is to sit tight and buy nothing till this settles down.
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Steve
WA6ZFT
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Re: f_T fixture and cheap transistors [long]
Here it is:
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73, Mike AF7KR
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Re: ADC Project Status, Fake Parts, Varactor Diodes and then Chinese Critter Checker[long]
Chuck
I had a similar experience to your fake FET's except mine were fake BF245A's. I got a refund by sending a picture of my component tester's BJT display. The generic NPN's that they had sent seem okay as audio/low frequency transistors although I have managed to get one to work in a crystal oscillator at 10MHz. I had only ordered 40 and have so far used up maybe 1/3 in various non critical circuits, My theory is that they sent the lowest cost BJT transistors they could get in the same style package as the BF245A's.
I can't help thinking that these guys must operate on razer thin margins for the cost difference between BJT's and FET's to make such substitutions viable for them.
I test every transistor and FET I get this way now. I find that I get maybe 1 in 10 or 20 that just don't work at all. It's been suggested to me that what they are selling are devices that fail the full manufacturers specification test. In many cases that failure doesn't stop it working in our circuits.. If we were manufacturers however we couldn't use them. It reminds me of purchases I made in the 60's and 70's when transistors were expensive. You used to be able to purchases packs of transistors labelled as manufacturers seconds.
Having said all of this its worth mentioning that there are examples of improved devices purchased from the same source. I always found the original LM386's not very good due to noise and second harmonic distortion plus a strong tendency to oscillate. Recently I have purchased what must be a new version of the LM386 with low noise and low distortion which is also stable. I have had a similar experience with 555 timers. Np one seems to be mentioning it, but I guess if you were designing these chips today you could made much better versions.
73
Mark VK6WV
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ADC Project Status, Fake Parts, Varactor Diodes and then Chinese Critter Checker[long]
Delayed in getting to build second ADC xcvr prototype because a package of J310s has
gone across the country and back for more than a week and having trouble
getting to me.? Hopefully by Monday.? Then I'll build the second prototype
to finish the complete manual and finalize the board layout.
Speaking of boards.? What is going to be the economics now of getting
PCBWay or other boards from China?? Inquiring minds want to know.
Start a new topic heading on the subject, please.
<> is what I call the
Chinese Critter Checker.? This one from NJ distributor.? Today's
price is $16.49 with case and free shipping.? If a number of
you rush to get one, then we'll see if price gouging kicks in.
And the blame goes to tariffing.
This critter saved me yesterday.? I'd been getting parts via
Eliexpress with a 100% success rate until yesterday when I got
a batch of 'BF245B' JFETs.? Turns out to be plain NPN BJTs.
The CCC caught it and I then went and found a simple test
<>
also confirmed the package as fakes.? Since they are BJTs, I'll run them through
the f_T tests to see if they are useable as just plain transistors at RF.
Otherwise, I'll test them for audio amp use.
Good news.? Got immediate refund and the vendor disappeared
from any listings.? Looks like they, Aliexpress, run a tight ship.? IMHO.
YMMV.
I asked DeepSeek why the significant price differential for BJT and JFETs and it
gave me a very detailed explanation. Just gotta love AI.
OK. Back to the bench.? 17m hasn't been the greatest the last few
days.? Someone mentioned QRP on 160m.? In my entire life I have
never worked a single station on 80m, much less 160m, using
QRP power.? Thus, no one ever on 80m.? Even when I had a 40m
vee beam at Prescott AZ.? Some magic must be involved, even when
the band is open.? NN1G had a cute little 80m transceiver in QRP Quarterly
that I wanted to try, but never got around to it.
I think Doug, KI6DS, started the question of VFO frequency change
using a 1N4004 or varactor diodes.? I did a series of measurements
in the K7QO/AA7FO QRP Lab Notebook <> (404 pages and
growing) on pages 233-248 on varactor diode measurements.? Will add
various other diodes when I get another fixture built for the LC-200A.
FYI,
--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
PA,CA,CO,WI,NE,ID,IL,NC,NY,WV
MA,OH,OR,RI,MT,WY,WA
DXCC W,VE,JA,PY,ZL
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I quick look at the AE marketplace reveals ample supplies of 4MHz crystals.? That with a 2-to-2.2MHz VFO would tune it down to the 160M band.? There is also a 4.433MHz HC-49s crystal offer, but 3x pricier.? But it would raise the VFO frequency up to 2.433-to-2.633 and further away from the 160M band.? Howard, n3fel
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Howard
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you have a fantastic idea. Avoid an IF that is a multiple of 1.8. Sounds pretty easy. While TR signal should work I wonder if it might carry transmit RF leakage? ?You may have to experiment some. Peek at K2 receive antenna board for design hints.?
Curt
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Good morning, all.? I'm thinking about a 160M build using one of my leftover NC40A boards.?
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I actually only need the receive side but with a bit more work can eventually get a complete transceiver.? For now, I could build and test the receiver first, leaving the TX circuitry unpopulated.? ?
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The mute circuit is critical as it would coexist with my QRO rig on 160 using just a LoG RX antenna.? My keyer can output a PTT signal to control it.?
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I'd need a common xtal frequency and a practical VFO tuning range to make this operable in the CW portion of the band.
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Has anyone tried it?? Howard, n3fel
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Re: QRP TX LPF illustration (30M built)
Also if you notice I widened the sweep this time to include the 4th harmonic which shows up about the same level as the 2nd harmonic. I imagine the other filters show the same for the 4th harmonic. (Filter sweep included again.)
Steve
toggle quoted message
Show quoted text
On 5/1/2025 5:39 PM, Steve Ratzlaff via groups.io wrote: I built the 30M W5USJ LPF from the chart, next. You'll notice on the chart that the input and output impedances for this filter are close to 50 ohms with little differences. My tests showed the same--45 Vpp? (5W) output either way. That indicates if one can design the trap filter for close to 50 ohms, then the filter is indeed symmetrical. Too bad Chuck Carpenter is not still around so we could ask him if he noticed the impedances were the same for this filter and not as close to 50 ohms for the others.
73,
Steve AA7U
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Re: QRP TX LPF illustration (30M built)
I built the 30M W5USJ LPF from the chart, next. You'll notice on the chart that the input and output impedances for this filter are close to 50 ohms with little differences. My tests showed the same--45 Vpp? (5W) output either way. That indicates if one can design the trap filter for close to 50 ohms, then the filter is indeed symmetrical. Too bad Chuck Carpenter is not still around so we could ask him if he noticed the impedances were the same for this filter and not as close to 50 ohms for the others.
73,
Steve AA7U
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Re: QRP TX LPF illustration
Hi,
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A while back, I noticed the familiar double-pi filter circuit that¡¯s often used at output of transmitters. One day, I did some calculations and realized the connection between the values of L and C¡¯s (each ¡°pi¡± filter has an inductance L in series and two C¡¯s in shunt at each end). For each pi filter, at the frequency at which a tank of L and C (mounted in parallel) meaning L*C*(w^2) = 1, the impedance as seen at the input is equal to the inverse of the impedance of the load at the output, times L divided by C. Stacking two of these pi filters in series, the input impedance is equal to the load impedance (again, this is at the frequency which L and C resonates).
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I made a video (poor quality, sorry about it), it describes the gists of the above explanation:
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When an inductor L is substituted by a parallel L¡¯/C¡¯, as long as the impedance of the L¡¯/C¡¯ is equal to that of the original L, the transformation of impedance (from load to input) at the frequency of interest still stays the same. However, the parallel L¡¯/C¡¯ would block the frequency at which they resonate at. This can be used to reduce substantially a harmonic of the frequency of interest.
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Values of L and C are chosen with considerations of maximum of voltage across the capacitor at the middle (2 of C¡¯s) and the currents that flow through the inductors L¡¯s and C¡¯s. Higher currents would make the filter having larger ohmic loss. Too high of a voltage mike blow capacitors.
I simulated in LTSpice and described this half-wave filter here (the article is in Vietnamese but you can ask Safari to auto-translate to English, it¡¯s not 100% but close enough):?
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Thang Le
AA6SV
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Kirk Kleinschmidt, NT0Z
Barb WB2CBA
k6whp
hwstar
