Desperation often leads to innovation, so they say. My order for a QRP-Labs QMX radio is so far down the waiting list that I won’t take delivery for several months yet. Why is it that some QRP radio manufacturers have such long waiting lists for their products? It could be that their products are very popular. Maybe that’s part of the reason, but I suspect the main reason is that they are owned and operated by engineers instead of business people. I have worked as an electronics engineer and I have been a small business owner. I am now retired, but I know how I would resolve the situation so that my customers would receive timely delivery of their orders.
I enjoy QRP but I know that I could walk into my local ham radio retailer and walk out with a QRO radio right away – no waiting.
So, with that rant out of the way, let me tell you how I brought another of my old QRP radios back into service.
The radio is a Hendricks PFR-3 (PFR: Personal Field Radio). I bought it from local ham (who is now sadly SK). He had assembled the radio from a kit in 2008 and had made regular use of it while traveling.
I used my PFR-3 for a couple of years, then it lay on a shelf in my shack for an extended period. Recently, out of desperation, I picked it up, dusted it off and powered it up to check if it was still alive.
The PFR-3 is a rather unique design. It incorporates a built-in manual tuner with an LED SWR indicator. There are two variable capacitors and a fixed inductor in the circuit. The two varicaps are adjusted until the LED dims, or extinguishes completely. Band selection is by means of two slide switches; the PFR-3 supports the 20m, 30m and 40m bands. Tuning is accomplished by two pushbutton switches – tune up and tune down, although later models had a rotary encoder instead.
The radio was originally equipped with an internal battery pack, making it a standalone rig – simply connect an antenna, key and headphones and away you go. However, to change the batteries it was necessary to remove four tiny screws to open the case then remove and replace the AA cells. I did not want to have to do this in the field. So, I built my own external power packs using readily available 18650 Li-Ion cells in 3S1P configuration. There are two packs, each securely housed inside aluminum Hammond enclosures. The enclosures protect the cells from damage (which can cause fire or explosion in Li-Ion cells). Fortunately, the two Hammond enclosures, side-by-side, have almost exactly the same footprint as the radio itself. A BMS (Battery Management System) circuit board is installed inside each pack mainly to protect the cells from being discharged too deeply.
The packs are charged using another DIY solution. It is recommended that only an approved charger should be used, but careful study of the charging characteristics of Lithium-Ion batteries revealed that they can be safely charged without one. The charging regimen involves a constant voltage phase to bring the charge up to near maximum. Then a second charge using constant current brings the battery up to 100%. One source suggested that the life of the cells would be extended if they are not repeatedly charged to 100%. Following this advice I use a regulated 13.8V bench supply with a buck converter to produce a constant voltage of 12.6V. I omit the constant current second phase. The battery may have less than its nominal amp-hour rate but the energy density of Li-Ion cells is way more than sufficient to power the PFR-3 which draws 45mA on receive and 750mA on transmit. Finally, I removed the original barrel connector from the radio and converted it to powerpoles.
I made a few brief contacts with my rejuvenated PFR-3 from my backyard, but the real test was whether it had what it takes to do a Parks on the Air activation. I wasn’t sure so I took along my Yaesu FT-891 kit – just in case. I should have had more faith in the old QRP rig, it completed an activation with no problem at all. In fact, I even logged a contact in the UK with it.
So, until that distant day when the aforementioned brand new QRP radio arrives, my 15 year-old Hendricks PFR-3 joins my 22 year-old Yaesu FT-817 in the QRP stable. Neither radio is sufficiently long-in-the-tooth to qualify as a boat anchor yet – but they aren’t far off.
The POTA Activation Using the Hendricks PFR-3
I chose the Lions Head Provincial Park (POTA ref: VE-0271) on the Georgian Bay shore of Ontario’s beautiful Bruce Peninsula to test the PFR-3’s cajones. This is an extremely popular and very busy park, but this trip was out of season and the park was quiet. Surprisingly, I am the only ham ever to have activated this popular park. The park – and the nearby village – get their name from a rock formation resembling the head of a lion on the cliffs at the entrance to the harbor. The provincial park is located on top of the cliffs. The location is also right on the Bruce Trail (VE-5628) and is part of the Niagara Escarpment Biosphere Reserve (VE-0063) making any activation a “3-fer” – yet still nobody else has activated it! If any reader wants to go there, contact me first; I can recommend an activation site in the park that is away from the summer crowds and over-subscribed parking – my secret, but I’m willing to share.
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