ARC-5 for casual AM/CW?

Discussion in 'Homebrew and Kit Projects' started by KD8NPB, Nov 29, 2011.

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  1. KD8NPB

    KD8NPB Ham Member QRZ Page

    The ARC-5 series seem like pretty fun little rigs to operate.

    How are they on AM/CW?

    They seem easy enough to run. I wouldn't mind owning the transmitter/receiver combos for 80m and 40m.

    Plus, doing a homebrew modulator seems like a lot of fun as well!
  2. K9STH

    K9STH Ham Member QRZ Page

    I have had a BC-454 receiver for decades. That is the 3.0 MHz to 6.0 MHz version. The receiver is sensitive and sounds fine on AM. It also works OK on CW. However, the bandwidth is pretty wide and people who are used to having narrow bandwidth filters will not like the performance on CW when the bands are crowded. However, when compared to most receivers of the late 1940s and well into the 1950s, the bandwidth is no worse than many, and slightly better than some.

    There were a lot of the ARC-5 / SCR-274N receivers used by amateur radio operators during the late 1940s and the early 1950s.

    Glen, K9STH
  3. KD8NPB

    KD8NPB Ham Member QRZ Page

    Wonderful. What all mods were done to the receiver?

    Wide CW...I laughed.

    Reminds me of me getting chewed out on 10m because my FT101EE drifted off frequency by a few hundred hertz.

    "Well darn it, you're off frequency again...did you bump the VFO or something?"

    I don't always have time to pre-heat my equipment for 30 minutes. :p

    They're pretty inexpensive. It seems as though I can pick up ARC-5 sets for $50-$75 each on eBay all day long.
  4. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I used an ARC5 receiver with a multiband HF converter as part of a mobile CW rig back in the late 60's. Most of the time, I was on 40 meters in the daytime, so I didn't encounter crowded band conditions. For what it was, it worked fine. Other than wiring it up to a mobile power supply (an old Heathkit), and adding a gear reduction knob to the main tuning, I am not aware of any big modifications, but I didn't set it up initially, either.
  5. K9STH

    K9STH Ham Member QRZ Page

    The heater string was rewired from 24 volts series/parallel to 12 volts parallel. Then the adapter box (the box that plugs into the front of the receiver) was disassembled and the front plate was used to mount a switch to turn on the BFO, a potentiometer to control the gain, and a headphone jack. All of the connections needed for these are found on the pins that the adapter box plugged into.

    You don't need more than 150 volts DC to run the receiver and even as little as 100 volts works fine. Of course, that is in addition to the 12 volts for the tube heaters.

    Some people just put in 6 volt equivalent tubes in the unit and then run 12 volts instead of 24 volts. Others change the heater wiring to parallel and then replace the 12 volt tubes with 6 volt version and then run 6 volts for the heaters.

    The same modifications work with all of the Command Set receivers, both the ARC-5 and the SCR-274N versions.

    I believe in the KISS principle and therefore did only the minimum required to get the receiver operating.

    Glen, K9STH
  6. W4HAY

    W4HAY Ham Member QRZ Page

    Just leave the filaments as-is and get a 24 Volt transformer from Radio Shack. As a matter of fact, get two and hook them back-to-back with a bridge rectifier on the second transformer for the B+. The receiver will draw about 40-50 MA at 180 Volts. Filament draw with the tubes in their original configuration is about 1/2 Amp.

    Forget the transmitter. It requires extensive modifications and shielding to get rid of the TVI. It's a beast to tame.

    There are (or were) sites on the internet that described the modifications we used to make to use them in our Novice stations.
  7. WA7KKP

    WA7KKP Ham Member QRZ Page

    My OM W7YZQ had an SCR-274 set for 75 meters; and a second 'transmitter' which was rebuilt into a modulator using the 1625's and a pretty hefty transformer. As per previous posts, the receiver selectivity was way to broad for crowded bands, but you could build a mixer from the IF down to another ARC-5 (the BC-453, aka Q-5er) which could get you pretty good selectivity at 85 kHz.

    The prices you quote for getting that gear is IMHO a bit out of the park -- I'd firmly recommend finding your projects at hamfest flea markets, where the prices are far less than E-pay. I find it hard to believe that after 66 years you can still find virgin receivers and transmitters in some places.

    Gary WA7KKP
  8. KL7AJ

    KL7AJ Ham Member QRZ Page

    The ARC-5 was what launched me on my ham career. I had two of them, one for 3-6Mc, and the other for 6-9 Mc. As broad as a barn door, but more then sensitive enough for real hamming. No volume control...just R.F. gain. No AGC. Raw and wonderful. :)
  9. W5QWX

    W5QWX XML Subscriber QRZ Page

    In the late 50s early 60s I ran the ARC-5 transmitters on CW then built modulators (a pair of 6146s) and used on AM. They were plentiful and cheap when bought from the surplus stores. An old buddy of mine W7RTC now AA1DH, helped convert a couple to DSB by PP modulating the screens of the 1625s with the PP output. Worked very well and had fair carrier suppression.
    I also made several VFOs out of the ACR-5 for other non-VFO controlled transmitters like the DX-60 and others of the time. Never used the ARC-5 receivers because the were always a coil turn or two broader than the Hammarlunds and Nationals I had back then. They are fun to play with and if you ever have a need for an analog VFO, they can't be beat as long as you have a stable power source.
    Just a super way to enjoy the circuits of the past.
  10. K9STH

    K9STH Ham Member QRZ Page

    I used a BC-459 (6.0 MHz to 9.1 MHz) transmitter for a VFO on 6-meters. Ran it into my Heath DX-20, yes, DX-20! All that it takes to modify the DX-20 for 6-meters is a piece of solid wire about 5 inches long and a single solder joint! When the band switch is in the 15-meter position, an 8.400 MHz crystal will triple to 25.200 MHz. Then the final amplifier doubles to 50.400 MHz. The DX-20 doubles in the final for 10-meters. The wire is used to short out most of the turns on the final tank coil. I plate modulated the DX-20 with a home brew push-pull 6L6 modulator.

    There was a local Technician Class operator who had the matching Gonset VFO for the Communicator III. He was "king of the hill" on 6-meters because everyone else had crystal control only. When I suddenly appeared with a VFO, and the DX-20 ran almost twice the power output of the Communicator III, the other operator refused to work me for well over 6-months! Finally, he realized that I was in no way trying to compete with him, just was using the VFO to work stations a lot faster.

    Glen, K9STH
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