PFR-3 Kit Build

Dear All

Excuse the bandwidth but some people have expressed an interest in how my build of the PFR-3 kit goes. It looks like it will be an excellent SOTA rig.

I started building it last night and spent about 4 hours during which time I completed and tested the Group 1 components (processor and display) and nearly completed Group 2 (receiver).

It’s going well and is not difficult even though I’m not a natural kit builder. In fact here is a photo of the successful “Group 1 smoke test” …already tuned to 7.032 :slight_smile:

More to do tonight with quite a lot of “toroid winding” arghh… :slight_smile:

I’ll post picture of each completed group as I go along (there are 5 to complete)

73 Marc G0AZS

In reply to G0AZS:

Great Marc, looking forward to read more soon :wink:

gl, Mario

In reply to G0AZS:

Great work, Marc. I’m about to complete a RockMite 20. I’ve been building this rig for about 2 weeks! It’s difficult to find the time, and even small tasks seem to take ages! Today I’ve mounted the PCB in the ‘statutory’ Altoids tin and I’m about half way through wiring up the connectors. Hopefully it’ll be up and running at weekend.

I can appreciate what is involved in building kits, and although it is actually quite simple, there is often more work involved than meets the eye!

Good luck with the kit!

Colin M0CGH

In reply to M0CGH:

Keep at it Colin, my RockMite 40 is fun!

Anyway, Group 2 (Receiver) completed tonight… although it took longer than anticipated. I’ve never wound toroids before and it didn’t go well at first!

Will do Group 2 smoke test (frequency calibration, IF offset and BFO adjust etc) and next picture tomorrow.

Phew… 73 Marc G0AZS

In reply to G0AZS:

Hi Marc,

Managed to sneak in an hour of RockMite construction this morning, so the rig is now finished. I fired the rig up and it appears to work! I have yet to wire up my straight key with a mono 3.5mm plug to put the rig into straight key mode. At the moment it just produces a stream of ‘dits’ when the straight key is pressed as I have it wired for the FT817 with a stereo plug. I’ve not tried the rig with an antenna yet, just a dummy load, but the sidetone sounds good in the headphones.

My next job is to make up a portable dipole cut for 14.060 MHz. I was hoping to go to York radio rally this weekend to get some supplies (Balun, RG174 etc), but money is tight!

I’ve put a pic of my RockMite 20 on Flickr (it looks like a clone of all the other RockMites!).


Hope the smoke test went ok, I didn’t try my rig until it was finished and in the tin!

73 Colin

In reply to M0CGH:
The Rock Mite looks nice Colin… well done.

Group 2 test and calibration on hold… took a break this evening to get familiar with Spectrogram software before calibration.

But I have to get this finished before my SM trip in a couple of weeks. Must crack on tomorrow.

73 Marc G0AZS


Group 2 now complete and smoke tested. RX peaks OK and I’m hearing signals fine on 40m.

I also used my 706 and WWV to calibrate the PFR-3 reference frequency and then used Spectrogram to do IF offset adjustments and BFO setting.

It’s all looking good at the moment and I’m getting more excited about using it in the field and on the trip to SM… here is the latest photo:

73 Marc G0AZS

In reply to G0AZS:

Hi Marc, glad to see the build is going ok.

I powered up the RockMite 20 last night and made up a lead for the straight key. Everything appears to work as it should. I tuned into the RockMite’s signal with my ft817, it would appear as though the RockMite operates on about 14.058 MHz. The CW tone sounded ok on the 817, so I’m very pleased with this project.

The next milestone will be it’s first QSO!

I have just acquired another Altoids tin which had belonged to my late Grandma, so I’ll have to build another QRP rig now!

Put another pic on flickr showing a comparison between my other home built rig, the Sparkford and the RockMite. The Sparkford cost about twice as much as RockMite to build, but the RockMite is my favourite!


73 Colin

In reply to M0CGH:

…it would appear as though the RockMite operates on about 14.058 MHz.

Hi Colin

Interestingly my “7.030” RockMite actually operates on 7.028 (and 7.0287 with the offset) which is quite normal with the current crystals according to Dave at Small Wonder.

Good luck with the first QSO’s.

73 Marc G0AZS

In reply to M0CGH:

This is what you need Colin…



PFR-3, group 3 components (transmitter) completed and initial smoke test OK.

Things are looking good with only 2 more groups to do and then boxing it up… maybe I’ll be able to give it an airing within a week or so.

Here is the latest picture:

73 Marc G0AZS


Group 4 components (low pass filters) complete. Here is the latest photo:

(yes I know there are a couple of leads to trim)

Astute observers will also note that a capacitor has “moved” in the receiver section. I had used the wrong value (should have read the errata) and got a little wound up when removing it… but it all turned out OK in the end.

The other thing is the fact that you can’t see the 8 toroids that have been wound and mounted on the back of the board. It really wasn’t difficult. I can’t see what the fuss is about. No need to worry about them at all.

Just group 5 (Tuner and SWR bridge) to do and it’s done.

73 Marc G0AZS


Group 5 (i.e. entire board) complete.

Power output tested at 5W (with 8 AA batteries) on 40, 30 and 20m.

I just need to put it in “the yellow case” now and then I will write a fuller report about the whole process when I’ve put it on the air.

Here is the last board only picture from the front:

…and here is the back.

The only toroid that caused me problems was L3, the large one for the tuner… and only because I didn’t read the instructions properly.

73 Marc G0AZS

In reply to G0AZS:
Looks very good Marc. I look forward to hearing how you got on with it “on air”

Roger MW0IDX


Short delay but it’s now finished and boxed up. I’ll write up a full report when I’ve done the first activation but here it is:

…and the rear:

…and an idea of size:

Amazing to think that all I need now in the field is my key and an antenna and away I go with 5W on 3 bands. What a great radio and such good value too!

73 Marc G0AZS

In reply to G0AZS:
Nice work Marc, I have just orded my kit and now waiting to get started.
It will be important to read your report of comments before I start my building of the cw-rig
Best 73 and hope to work you from a swedish summit with this rig

So as promised, here is a more comprehensive review of how I built and used the PFR-3 for the first time.

I saw the first news about the PFR-3 earlier this year but had to wait until mid May before I could order one… which I duly did the day the on-line order form opened on I had to wait a while and my kit arrived in mid June.

The reason I chose it is because of its “all in one” design. I have an ATS-3B kit that I was about to build but this seemed to be better for what I wanted i.e. A radio to take on SOTA activations and one that could travel with me pretty much wherever I want.

The “interesting” specifications for me are as follows:

5W output on 40, 30 and 20m
Built in tuner (coax and balanced inputs)
Built in absorptive SWR bridge (don’t blow your finals when tuning)
300 Hz narrow filter
Memory keyer
Built in battery supply if needed.

This is not an exhaustive list of the features but they were the ones that I particularly liked.

All this for $220 including delivery to the UK. This worked out at £117 (€150) delivered!

Note that kits are exempt from import duty to the EU but you MAY get charged VAT… sometimes you get charged… sometimes not. It depends on how vigilant the post office is being.

I started building it a couple of weeks ago to be ready for my SM trip next week. I had to wait because the firmware was updated due to some minor bugs and my kit had the initial firmware on the chip. The vendors assured everyone their chips could be reprogrammed free of charge if they were sent back to the designer. I contacted him - Steve Weber, KD1JV and asked if he could rush the new one back when he had received the old one. He did better than that; he sent me a new one, trusting that I would put the old one in the post… great service!

Note that I’m not a natural builder and the times given below are genuine for me working at a careful, steady pace. I’m sure others could go quicker.

The build started well. Group 1 is related to the microprocessor and display. Note that the SMD’s were already mounted on the board… no need to worry about them. Testing this group is basically looking for a working display. Then you listen for the processor radiating somewhere near 2.115Mhz on a receiver.

I spent about 3 hours on preparation and group 1 build.

Group 2, the receiver, was also straightforward to assemble although there are couple of toroids to wind with 40 turns each. I had never wound any before and was a little nervous but it went fine. Actually I quite enjoyed it!

The smoke test for group 2 is all about reference frequency alignment and filter and BFO adjustment. I don’t have a frequency counter or an oscilloscope. But you probably have a receiver for 10MHz (WWV) and a PC where you can install spectrogram, then you will find it’s dead easy to get it aligned very well. I think I ended up within about 20Hz of where I should have been on 40m with filter centred and BFO aligned.

I spent about 3 hours on build and alignment for group 2.

Group 3, transmitter, was also easy with just 1 small toroid to wind. An easy test and then I moved on to Group 4, low pass filters, which required winding 6 toroids. Again it was easy and quite therapeutic listening to the radio.

These 2 groups took me about 4 hours altogether.

Group 5, the SWR bridge and tuner, is the last board construction step. This went fine although I wound L3, the large tuner toroid, the wrong way round. I had to unwind it and start again,. I had become rather lax and didn’t read the instructions properly. By the time I had rewound it, loads of time had passed and it was getting rather late so I rushed mounting it. I knew that I hadn’t prepared the leads well and I could see a “dry joint” or two.

So the following day I unsoldered L3, rewound it and adjusted the number of turns with the latest recommendations. This time it soldered in just fine and I fired the board up for a first power check. I was pleased to see about 5.5W on 40m and 30m and about 4.5W on 20m. I adjusted the power up to 5W on 20m by spacing the coils on a couple of toroids.

I spent about 4 hours on this group although I wasted a lot of time. It should have taken 2 hours or less.

The final step was boxing it all up. The hardware supplied with the kit is fine and, although some might think the yellow box is odd, I love it!

Boxing it and tidying it up took me about 2 hours

So today I finally started trying things out to see what it’s capable of. Now one thing to note is the fact that the tuner will not match everything. It really has been optimised for the 44ft Norcal doublet. I tried it on my G5RV at home and it would tune on 30 and 20m but not 40m.

When out this afternoon I was using my “double Norcal doublet” 88ft long and that tuned up just fine on all bands. I would imagine that a 44ft one would be fine as well. You can also use the tuner to tune coax fed antennas and long wire plus counterpoise as well.

Tuning is easy. You put the switch in the tune position, send a few dashs and try to dim the LED by moving the tune and load knobs. The LED is actually VERY bright… it was no problem in the sun and I think it would ruin your night vision! The tuning is quite sharp but it will go out completely when there is a perfect match. (I checked it with a dummy load beforehand so I could see how dim it got)

Tuning frequency with the buttons takes some getting used to. It moves 50Hz with each click and faster when you hold them down. You shouldn’t tune too fast as the filter bandwidth is only 300Hz so you could easily miss someone.

Changing bands requires that you move 2 switches. This might seem like a pain but it’s not and I can’t believe anyone would forget this. You also have to peak the receiver but this is also quick.

When I used the PFR-3 this afternoon for activation on G/CE-005, I just used the internal 8 x AA batteries (which were not fresh) so I would imagine I was probably radiating about 4W or so. I might carry a small SLAB and just use the internal batteries for emergency back up.

Stations calling were easy to copy although it took me a while to get used to the lack of AGC and remember that I could turn up the volume if a weak station was quiet.

I didn’t set up the memory keyer and it took me a few QSO’s to get used to the way the built-in Iambic keyer behaved (did you notice!). It “feels” different to the one on the 706. I was using Iambic mode A but you have the choice of mode B as well. I was running it at 20wpm (indicated on the display).

I’m very pleased with the rig on the first activation and, by the way, the all up weight of the rig with batteries loaded is 725g. Just take along a key, headphones and a light antenna and you are in business!

You will find all the build photos in my Flickr photostream here:

I will definitely take this rig to SM for the IOTA contest (QRP section) from EU-037 as SM7ZAU and, hopefully, the activation of Kullaberg SM/SE-001 on Friday (weather and travel schedule permitting) as SM7ZAU/P.

If anyone has any specific questions or comments on the build or this afternoon’s performance, I would be very happy to hear from you.

73 Marc G0AZS

In reply to G0AZS:
Hello Marc
Thank´s for very interesting info. I am still waiting for my PFR-3 kit and I hope it will be here soon.
What time do you expect to be on Kullaberg om Friday? I will stop with my caravan close to Höganäs on Friday evening to spend some days at Örestrand, a youth camp in Strandbaden.It would be very nice to meet you if it is possible.
73 de Mats SM7BUA