A Curious 9 MHz Crystal from Mouser Electronics

Just a quick post to share info about a good 9 MHz crystal sold by Mouser Electronics.

I last purchased batches of crystals for xtal IF filters back in 2014. Since then, I’ve bought various 1 off xtals for micro controller clocks, but these were never critical parts. Now in 2025, I felt a freeze frame effect – a huge difference – Crystals cost more, less IF choices seem available; and now, the mini- HC49 or SMD versions seems more popular than the full size HC49 variants. All this makes sense in a SMD/digital world.

Further, I randomly swept some of the smaller sized rocks that I had ~recently ordered and I seemed to see more spurs, plus, low Qul (< 70K in 3 cases ) -- at least in the handful of crystals that I tested.Your own results may vary.

I've already wrote about worsening access to xtals for filters in some areas of the world – we are pampered with Mouser and Digi-Key in North America. In parts of Eastern Europe where I have a couple of contacts, some analog builders find 3 or 4 xtals that are the same frequency inside a bunch of old computers and desolder them. Forget about frequency matching multiple xtals – that’s for “ rich people”. 

Today, If you count currency exchange, shipping and perhaps tariffs, this rings even truer. The days of ordering a batch of 35-40 crystals to make "1 good“ crystal filter seems a costly adventure for some builders.

I wanted to ply a specific 9 MHz crystal made by IQD - their 449-LFXTAL064523BULK (Mouser Electronics number). I wanted a maximum of 3 crystals in my filter – also 1 for the BFO. I prefer less poles – plus also a BW of 400 - 500 Hz for my CW receivers. I detest aural ringing from group delay in my xtal filters. 

In my active audio filters, I now choose a Bessell response to get a maximally flat group delay to give you some added context about my preferences regarding filter group delay.

IQD 449-LFXTAL064523BULK

How did I learn about this particular crystal? On his website, Wes has pdf files on how to make crystal ladder filters. 1 of them is a file about making simple 9 MHz crystal filters – he actually relaxes a little bit on the equations/math for newcomers on this file -- and it’s a great file. Thanks Wes! 

The 9 MHz crystal Wes uses on this paper is this particular Mouser part: 449-LFXTAL064523BULK . When I ordered them on Feb 5^th – they had only 3 in stock !!! My xtal filter was made from those 3 crystals that arrived 2 days later.

I also had other IQD (Wurth Electronics) crystals in other frequencies ordered from Mouser long ago including 7.68 MHz, 7.3728 MHz, 4.9152 MHz and 2 other frequencies, so I felt confident IQD crystals are both suitable + economical for RF experimenters like me.

Before I measured my xtal parameters using the G3UUR method plus hand calculations. I exactly copied Wes’ simple CW filter capacitor values as a curious experiment. Wes only showed simulations – however, from experience; software can not simulate all the stray capacitance from the IF amp, coils, connectors, etc. But it’s close enough for jazz.

Above — Snippet of my IF stage within my receiver. Filter input /output Z = 50 Ω .

Above — Sweep of my 3 xtal filter.  Span = 40 KHz  Bandwidth = 449 Hertz due to different crystal parameters than the source article - but still OK for me.

For 3 random crystals (unmatched) – I think it looks OK. The losses are over stated in my sweeper due to extra attenuator padding -- I carefully measured the filter insertion loss at 3.89 dB for these 3 random, unmatched crystals. 

 Above — Sweep of my 3 xtal filter.  Span = 10 KHz

 Back Order

At the time of my order, I also back ordered 20 more 449-LFXTAL064523BULK  crystals.

Mouser evidently orders these crystals in batches of 1K from their supplier. I feel glad that IQD (Wurth Electronics) are still making them. I received these 20 back-ordered crystals last week &  measured the Qul of 3 of my xtals which averaged ~135K. Good enough for CW and SSB filters alike. 
       
Curiously, when my xtals arrived on March 11, Mouser had 972 remaining in stock. When I checked again about 1 week later --- they had 0!  Mouser seemingly ordered another 1000 from the factory and they will arrive near the end of April. I wonder how long this stock will last?

If you need xtals for IF filters in future projects – perhaps now might be a time to buy some?

Best! 

Receiver LM386 and Audio PA Woes – my readers suffer and garner my empathy

Greetings and welcome!

I’ve blogged about the LM386 over 2 decades. I’ve received many 10s of emails where builders told me their problems with the LM386 IC ( and other AF power amps - including my designs ). Many seem bog standard concerns – such as motor boating, or excessive noise when the LM386 gets operated in high gain mode.

For other builders, their problems seemed to arise when they combine RF, plus high gain AF stages, and a PA like the LM386 within their radio receiver.
For sure, a solitary LM386 with reasonable low pass filtering on Pin 6 will generally behave nicely when tested on your bench. It usually sounds lovely if you bother to audio test it with recorded music through a speaker.

However, when you place that ol' LM386 in a direct conversion receiver with >= 80 dB AF gain, things might change. Noises such as “howling”, “hissing”, “wild oscillations”, “weird modulations”, “harsh noise emanation” – “especially when the audio gain is turned up” have all been described in emails.

Some builders run the receiver AF + RF stages on a home-designed, fabricated single PC board. Then they may connect a digital VFO to the LO port of the mixer ( and also perhaps use the same DDS as the BFO in superheterodyne receivers). These builders now have DC, digital, AF and RF circuits working with the same 0 volt ‘ground’ return path on their main receiver board.

Ground

Ground (as we mostly think of it) = a 0 volt reference and does not imply earth ground. Combining DC, RF, digital, AF voltage gain stages -- plus an AF power amp with the same return path on a single board may lead to disaster unless you are skilled at designing PC boards. People go to school to learn this stuff – especially in today’s digital electronics world where RF, DC, and high speed logic gates & oscillators all coexist.

Star Grounding

Some believe that star grounding ( defined as the parallel connection of isolated circuit board ground planes to a single 0 volt reference point ) will work when combining DC, RF, an AF power amp +/ a digital VFO. It might help in some cases, however, often it won’t.

Parallel single point “star” grounding generally works for signals less than 100 KHz; however @ RF – ‘ground wires & traces’ may cause a high inductive reactance RF ground return path. As you move up in frequency,  PC board traces & wires become transmission lines. At RF, these transmission lines may inductively or capacitively couple to other transmission lines, or nearby circuity, in what we often call cross talk.

Also at RF, grounding wires may exhibit capacitance and often enough, parasitic capacitance.

Sadly, some builders may also learn that high bandwidth noisy circuits may corrupt nearby low noise circuitry with all this unwanted coupling going on in their circuitry.

DC Supply Filtration or Battery?

Poorly filtered DC circuit paths may serve as a ‘freeway’ allowing noise, RF, AF and digital pulses to modulate other AC signals, or perhaps provide the needed phase shift from output to input to create an oscillator around amplifier stage(s) -- and really frustrate the home brew experience. I won’t even delve into the world of ground loops and hum – another nail biter.

Back to the single PC board builders who were not experienced in PC board design. To their credit, usually, their VFO was located in a separate box, albeit they seemingly rarely employed RF tight enclosures.

To solve their AF power amp woes, some of these builders – opted to power their PA such as the LM386 with a 9 volt battery cell (or other battery pack) and keeping the audio PA circuit a reasonable distance from their main receiver. Others went with a powered speaker. These might be the only practical solution for builders who made a single PC board receiver and could not get a stable audio power amp despite trying to patch the problem.

Yay 1970s

It’s so great to learn from the past and happily builders in the 1970’s knew how manage the LM386 -- but sadly, they didn’t make videos back then. In short, place your audio PA on a separate copper clad or printed circuit board with the ground wire returning to your single point 0 volt node on your receiver DC power buss. Filter the DC voltage going to pin 6 very well. E.g. solder a 470 to 1000 µF capacitor right on pin 6. You may also have to insert a series resistor such as 10 ohms between pin 6 and the DC supply to lower the RC low pass 3 dB cutoff frequency.

Keep the input circuitry away from the output circuitry. Watch that you don’t push too much low frequency or high frequency audio into the LM386 since these may increase instability, clipping and noise.

A well designed audio chain attenuates the low and high frequencies that we don’t need in our receive audio chain. Case in point – some builders prefer to make all discrete BJT audio stages – for example, with the 2N3904. This is OK, however, consider that the 2N3904 has an fT of 300 MHz and that we use this BJT as an RF amplifier @ HF.

At audio, a 2N3904 amp may offer the same gain at 1-2 KHz as it does at 40-50 KHz. Do you need high gain at 40-50 KHz in a communications receiver audio chain? Ideally, the audio gain should taper off as we move up in audio frequency to reduce the noise bandwidth, and to promote stability in the audio chain which includes our LM386. Added noise is always unwanted and in simple terms -- higher bandwidth means higher noise.

Some Hams and SWLs have normalized receiver wide band AF noise since even commercial gear makers may cut costs on their audio chains while focusing on the highly marketable, high dynamic range bleeding edge RF circuitry -- and beautiful, colorful waterfall displays.

For home brew – local and global amplifier negative feedback, AF low pass + some high pass filtration, careful layout with respect to inputs and outputs, strategies to reduce AF ground loops -- plus careful DC filtration will boost your chances of making stable, great sounding, receiver audio.

While HF construction is common, very few builders venture into VHF and UHF -- and some never acquire the hard-fought skills needed to successful lay out, shield and manage real and parasitic interfering currents with common RF return path circuitry. Once you’ve done work + measurement above 30 MHz, you tend to build every circuit like it operates at 1 GHz.

I encourage builders to venture into VHF and beyond. It’s great fun! 

A 7.X MHz receiver may be quite forgiving to sloppy construction, layout and DC filtration – great for new builders;   but perhaps less than ideal if you seek to truly learn radio craft and move beyond cook book / copyist status.

Whether you make digital, analog, or mixed-circuit radios that drive a speaker or headphones – basic rules apply & the laws of physicals don’t change.

 

Above — An LM386 with negative feedback ( 10K to 1 nF) to reduce audio bandwidth. Pin 6 features perhaps over-the-top DC filtration - an active low pass filter via the BD139.

I plan to experiment with this circuit  further -- and to measure the differences with distinct Pin 6 filter circuits. Meanwhile, I'm enjoying listening to monaural music through it.

 Above — DSO screen shot with LM386 driven to maximum clean output power @ 1 KHz

  Above — FFT with LM386 driven to 1 KHz maximum clean output power

 

Above — I tested many aspects of the LM386. For example: what happens when you bypass Pin 8 to ground. This drops the voltage gain by ~ 60% @ 1 KHz!  I also tested it with different speakers with different speaker efficiencies to measure the impacts on volume, stability and average current draw. 

I still love the LM386 despite it's ancient pedigree, input noise, and its many other warts.  Very few analog ICs enjoy such an amazing legacy. It's simply a fun part to experiment with -- and on which to learn our craft.

Best to you!

 

Another Look at the BFO from The Progressive Communications Receiver from QST for November 1981

The Progressive Communications Receiver from November 1981 written by Wes, W7ZOI and John, K5IRK provides 2 of my all-time favorite analog superhet circuits: The BFO and IF amp/AGC system exalt fabulous design and function. Later, Wes -- along with Jeff, WA7MLH seemingly evolved this IF system into the hybrid cascode version presented in QST for December 2007. 

I've built 4 versions of the HYCAS IF circuit, but, I won't lie -- I prefer the IF system from the Progressive Receiver -- & I collected dual gate MOSFETs to build it back in the day. Fantastica.

BFO

I sought a 9 MHz Beat Frequency Oscillator to switch a a diode ring product detector in a new, popcorn 9 MHz IF superheterodyne receiver.   I built a couple standard BFO designs, but didn't feel happy.
To get a 50 ohm output impedance with low distortion -- plus an available power output close to 7 dBm takes a lot of buffer stage current,  filtration & effort; at least for me.  On the other hand, to make a low distortion BFO for 0 to -10 dBm available power output seems easy.

Then I remembered the BFO from the Progressive Receiver. Just 1 transistor gets it done. Popcorn! The output AC voltage is in the order of 2.3 volts peak to peak -- and the harmonic distortion is relatively low; especially for a bipolar transistor amplifier since an oscillator with a BJT amp tends to clip quicker (or more abruptly) than a JFET amp oscillator.

Above — My take on the Progressive Receiver BFO. Although an excellent design, I have never exactly copied any circuit in my life. e.g. 'I am an experimenter'.  I removed the DC from the secondary, bumped up the base bias resistors to reduce current loss through the base bias network to ground -- and found that a 35 to 5 turns ratio gave slightly better output amplitude + distortion performance @ 9 MHz.

The output circuit is part of the feedback loop so a delicate dance ensues when tweaking this interesting design. Further, a pi low-pass filter was added (918 nH inductor wound on a T37-6 dust powder toroid). Additionally, using math or software + measurement, a builder could adapt this pi filter to perform impedance transformation to boost output return loss.

The output was buffered/padded with a 5 dB pad to give an output available power of 6.26 dBm. I tuned the oscillator output with a 68 pF plus a 2.2 pF in parallel after removing and measuring the variable trimmer capacitor ( 70 pF ) after peaking the output in my DSO.

Above — The raw output of the BFO into a 50 Ω  input impedance DSO.  The BNC output port was connected to the DSO with a 50 Ω  coaxial cable.

Above — A bench 6 dB 50 Ω attenuator pad was placed between the BFO output port and the 50 Ω coax going to the DSO.

Above —  The output of the circuit shown in the schematic. Likely, the low pass filter is not needed, however, I demand a 50% duty cycle from my BFO circuit to switch a diode ring mixer. You might argue that the raw, padded output is good enough. This is a genius design after all.

In BFOs circuits with 2 - 3 transistors getting a clean signal output usually takes >= 10 mA between the stages -- or a 5th order low pass filter to mop up the mess at the end. This circuit gets it done with a current draw of ~ 7.7 mA and minimal filtration. I'm happy.

FILTER DESIGN using Web tools

From site data analysis -- just over 50% of my readers do NOT use the Windows OS. They use Mac, Linux, Android and a myriad of other operating systems. Many hardcore security-biased builders choose not to use Windows emulators -- and thus cannot run Windows-based software.  I recently got a question from a Norwegian reader who uses Mac -- How do I design my filters?

I've built up a collection of useful web tools that improve my design workflow. These mostly run java script in your web browser. For filter design, I recommend the LC design system of Marki microwave. Click here for the link  

For example, here is a screen shot of the filter I used in the BFO:

Above — My filter design by Marki Microwave's tool. I manipulated the cutoff frequency to get standard value caps ( 330 pF ) and used the plot ( unshown) to check that S11 at 9 MHz was OK. The Marki microwave site, tutorials and products prove excellent. 

Thanks and best!!

Above — This week snow drops bloomed in the garden. In the foreground the cat mint is budding. Spring emanates.

Popcorn Electronics Email Address Change Reminder -- Thanks!

 Greetings ###

The old email server went down due to Winter storm ~ 2 weeks ago --- and AC power was restored to the property only today. Several radio-related emails were on the incoming server -- and perhaps others may have been missed due to the server shutting down after the U.P.S. battery eventually died.

-  That's why I did not reply to your email message -

The old server is only checked once per month now and will get phased out by the Equinox

Please remove my old email address from your email contact list -- and the previously sent email address that automatically comes up in the TO: line when you compose an email.  The new email account is via GMail.

Click for our current email address   

Many thanks and best regards!

Popcorn Todd 

PNP Transistor Radios — What your father knew but didn't tell you

Emailers have encouraged me to publish my off-cuts. About 50% of my ideas fail. This is a tough hobby grasshopper. I first chose to not publish my VHF PNP experiments from 2024 because few people ever make PNP transistor circuits --  and as the kids say; "like  - who cares?".  Perhaps no one indeed.  But here goes.

I love PNP circuits and the rich history they hold as radio transitioned from tube (valves for you Brits) to solid state design.

Solid state amateur home brew is ancient craft

In the 1960s, using small signal germanium transistors, home brewers were making single side band suppressed carrier transmitters + also receivers with crystal filters, phase-shift networks, & even Weaver networks.  Nothing new under the sun?

Above — Click to see a solid state complete 40 meter band SSB transceiver using a Collins mechanical filter for IF filtration. The A01 transistor and all others were PNP. Still, they got it done without all the fancy programs and test equipment we've got today. I feel humbled by old circuits like this. These images came from a printed book called the Transistor Radio Handbook. This serves as my all-time favorite radio book to read since forever.  Someone has it online here.   I treasure my printed copy.

 

Above — Inspired by this Figure, I decide to make a low current, PNP RF preamplifier for my battery operated weather receiver at 162.55 MHz. Please read - the Philco 2N1742 datasheet - an fT of 150 MHz -- and whoa, look at the current gain. I'll use a few more modern silicon BJTs in my design lol.  

I love silicon transistors -- although I once build a custom fuzz 'stomp box' for a professional guitarist using germanium transistors when I served as his (tube) amp tech.

 

From reading the  Transistor Radio handbook, even in the 1960's, home brew players had enough common sense to stick their projects in metal boxes and understood how to bypass and decouple their circuits.  Somehow, despite easy summations like Mark Montrose's book above, some modern analog builders seemingly feel that the laws of physics don't apply to their projects. Curious.

 

Above — My base schematic. A PNP preamp with tuned input + output, no negative feedback (or neutralization) and a collector current of 2.4 mA. I tried old-school neutralization as shown in the inspiration schematic , but found that tapping the output coil as shown worked much better to stabilize the amp.

Input Tank Circuit 

Above — Sweep of circuit adapted to allow assessment & tuning of the input tank circuit.

For the collector coil, I temporarily placed a FT-23-43 ferrite with 10 turns on it in-situ.  I shunted that coil with a 56 Ω resistor to give a decent output Z for my sweep circuit. Thus, I knew that the frequency transfer response was due the input circuit. I tweaked the trimmer capacitor so it peaked at 162.55 MHz.

Q1 = MPSH10, a 650 MHz part still surprisingly available in Mouser's catalog for 2025. Even with the "temporary" 56 Ω resistor | coil, this amp provides a power gain of  ~ 4.6 dB.

The rest of the circuit

 

Above — "Rookie mistake". To show what might happen if one decides to not include the 39 ohm 'UHF snubber' resistor on the collector,  plus -- not tapping the collector coil as performed in the original schematic.

 

Above — The transfer function of the original schematic as shown with a MPSH10 BJT. Love this.

Most modern builders would never put a BJT as a low noise amp in a VHF project. Plus they would run a lot of current for a high dynamic range.

BJTS at VHF and above bands in the 1960s led to JFETS -->MOSFETS -->GaAsFETS | MESFETS --> pHEMT and so forth over time. But, today, we are making battery powered radio circuitry & using BJTs circa 1963.  Feels refreshing.

 

 Above — What happens  when we stick in a 2N3906 PNP?  Power gain = 2.4 dB

 Above — My fastest leaded PNP part, the BF509 soldered into the Q1 slot.

 

Above — It's fun to read the datasheet of older parts. I've got several PNP SMD parts with an fT up to 9 GHz. Even most of these are obsolete and were collected years ago when parts were real ( not so bootlegged ) and relatively cheaper.

PNP circuits are really not that different or difficult than NPN circuits. I encourage you to experiment with PNP transistors for fun and learning.

Best to you --  Spring is coming!

 

Op-ed. Having fun and receiver performance are not always related -- The fate of analog-biased home brew radio --

 

I'm only guessing the date, but perhaps, sometime in the 1970s -- a portion of home brew and certainly the professional amateur radio industry pursued high dynamic range as the be-all, end-all for receivers.

1. Like most – I appreciate a sublimely quiet, high dynamic range receiver; especially on contest weekends. Imagine our “ideal receiver” -- one that that easily detects 2 or more desired signals with an amplitude difference of 90 or 100 dB with ultra low distortion. Then too, our perfect receiver provides ball-busting immunity to the spurious responses produced by the nonlinear interaction of multiple strong signals coming into our antenna with no sweat. Ooh la la .

We’re talking about amateur radio contest-grade receivers. You generally have to run lots more current, high amplitude local oscillators, spend more money on parts -- and perhaps apply more complex circuits to get towards our perfect, idealized receiver if you home brew this stuff.  Will the pursuit of high dynamic range receivers help our analog-biased home brew hobby survive a little bit longer?  Perhaps for some.

In Canada, from surveys and also from viewing the sea of grey-haired club Hams milling around at the Ham Fest / radio flea markets, the largest demographic are those Hams aged 60-80. Many of these folks still like CW, although the younger Hams don’t. It seems that the youngsters prefer voice modulation modes, plus they apparently favor battery powered, mobile rigs. All these points might prove good goals for home brew designers who hope to attract younger Hams into home brew.

A significant portion of the ‘old-timers’ are inactive – some haven’t fired up their rig(s) for decades. Not even on 2 meters.

I’ve chatted with a few of these ‘nearly, or totally silent folks’ (who still identify as Hams and come to larger amateur radio gatherings for social contact, community and to reminisce ), Why are they silent? The answer seems complex. Partly, it was the Internet which arrived here locally in 1995. Then perhaps -- smart phones, changing tastes, changing family-life priorities, home & yard downsizing, health concerns, the digital electronics age, plus ‘tens of billions or so’ competing leisure activities may have contributed to these folks giving up operating their radio sets. What about home brew? -- I’ve got no idea. All of this and more?

With emails and conversations, some entry-level analog-biased home brewers feel intimated by high performance, contest grade projects, or advanced test procedures. Not everyone wants to go in whole hog and learn stuff like small signal analysis, or C programming, how to solve complex equations in Python, or to measure noise figure

Newcomers face more practical tasks like finding truly knowledgeable, trustworthy Elmers & sourcing affordable parts in their country. Basic skills like soldering, how to make circuit boards and understanding how to wind transformers are all skills they need to learn. As with every other hobby, they must navigate through abundant online misinformation, big meanies, and hucksters.

At 1 time the Ham philosophy to just make do with surplus or cheap gear served us well. Like most hobbies, this morphed into consumerism -- better, faster, newer, more, more, more. Now, in the digital age – some potential builders feel even more like a fish out of water.

 

Further, the asynchronous nature or automation of Ham radio has put off a few people....  I recall 1 recent, very snarky email in particular; “While I slept for about 8 hours, 15 stations heard my beacon. Yippee!     Boy howdy,  has Ham radio ever gotten exciting!!!”

Maybe synchronous communication - actual rag chews on home brew gear will provide us something to talk about?!

For some older builders, having fun, re-purposing and being thrifty were key reasons they liked home brew and even Ham Radio in general. How do we reignite the home brew passion in those turned dispassionate, ‘silent’ 60-80 year olds? Perhaps it's a lost cause? Further, how do we recruit a few younger Hams into building some old-style analog-biased radio gear? What about the recruitment of bored baby boomers into amateur radio in general?

For ‘silent’ older Hams, I conjecture that complex rigs, or projects that require them to learn to compile code into a hex file and/or write some lines of code won’t likely help recruit them back into home brew radio.

Personally knowing about presbyopia first hand, should; or how will they learn how to build with SMD parts as certain leaded parts become expensive, hard to find, or bootleg?

These are topics perhaps the home brew community might think about.

On the other hand – cheap, powerful test equipment lies abundant. For example, low cost, hobby-grade vector network analyzers. Test equipment wise – it’s never been a better time to do home brew radio.

Perhaps simplicity, fun and thrift for newcomers, or re-comers will once again serve analog-biased home brew for a few more years?

With a simple, but good receivers, third order intercept point products normally lie below the receiver noise floor during casual listening. If the front end gets overloaded and pushes the receiver into non-linear operation, perhaps they might switch on an attenuator, or turn a potentiometer to hopefully re-establish linear function – or just have to cope. It’s not the end of the world.   Having fun and receiver performance are not always related.

• Am I active on the amateur bands??

• Am I having fun ??

  Might be the best 2 metrics to embrace. Who knows? Perhaps, I’ve got it wrong and demographics and technological advancements totally determines the fate of analog-biased home brew radio? Perhaps like the horse and buggy, amateur radio analog-biased home brew’s fate is sealed.

   

• Simple, but good gear

• Emphasize and teach quality basic measurement techniques

• Thrift

• Have fun

• Learn at your own pace

• Communicate

These 6 above bold themes will inform Popcorn Electronics video content going forward.

We’ve got a lot of newly or ‘newish’ retired boomers with time on their hands. Some of them might enjoy making some home brew analog radio gear. Kits are also an option.

Best!

My 3.5X MHz Voltage Tuned VFO -- Have I gone crazy?

 

 

My Voltage Tuned VFO - Have I gone crazy?

I built a 3.5X MHz scratch voltage controlled VFO for home brew radios. No PLL circuit -- a free running variable frequency oscillator. Have I gone mad?  Perhaps. Complete design + analysis, plus a short assessment of frequency stability due to temperature changes at 2 frequency bands.

* RESOURCES *

Brad's VFO Story  How to make a temperature stable VFO
https://youtu.be/kcc8V5IMmlw

SolderSmoke Daily News -- Ham Radio Blog
https://soldersmoke.blogspot.com/ 

Iulian, YO3DAC - VA3IUL Website

https://www.qsl.net/va3iul/