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Reviews For: Collins ARR-41 R648 Receiver

Category: Receivers: non-amateur adaptable for ham use

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Review Summary For : Collins ARR-41 R648 Receiver
Reviews: 3MSRP: unknown
Description:
190kHz-550kHz & 2MHz-25MHz receiver. Dual conversion except 2MHz-4MHz band. Two RF and three IF stages with 6.1kHz and 1.4kHz mechanical filters at IF of 500kHz. Full-time noise limiter (no off function) for AM & CW reception. Mechanical digital frequency readout and built-in crystal calibrator
Product is not in production
More Info: http://
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0035
AC2YW Rating: 2021-07-22
Rare work or art Time Owned: 3 to 6 months.
This receiver is similar to the R390, but much lighter and won't take up too much room on your desk. What's missing is a good choice in filters, audio filter, and the meters. The RF/Mix/IF is 6ba6/6be6, so not as sophisticated as the 390, but still uses high quality parts throughout. Besides the permeability and mechanical digital tuning, each module is a work of art in itself. If there's a problem, very little of the radio is accessible for live troubleshooting, however. Collins used a complicated scheme to save on the number of crystals and this design itself is a work of art. There's also a clever calibration circuit that calibrates while in AM mode, removing BFO error. The AM AGC is gated, making the radio sound quiet.

On the down side, it feels like Collins put loads of technology into an under-featured receiver. Also, the tuning is a bit stiff and tuning up and down the band is not as enjoyable as a conventional receiver. I've owned an R390 and thought it was smoother to tune, but this may vary from sample to sample. The AGC is for AM only, and for CW/SSB the gain is manual. The plus is just how good SSB can sound when you set the gain right. There's no SSB filter, but I hardly felt I needed one as the 6KHz AM filter works well enough in most situations. The 1.4 filter works for SSB but not worth using.

I replaced the dynamotor with a modified DC-DC converter available on eBay. These Chinese beauties need a couple of part substitutions to truly handle 24 or more volts. Some hash without a shield and no hash with one. This is the best way to go as the modification is very local compared to a 115V conversion.
KK7B Rating: 2018-09-10
Interesting old radio Time Owned: more than 12 months.
I've had several of these, and the R-648 was my primary station receiver from 1972 through 1979. I've built internal and external power supplies, and briefly run an all original one on the internal dynamotor. It was designed for airborne use in Naval aircraft, and dynamotor noise wouldn't be an issue in that environment. Build quality is similar to the R-390A, and the few front panel controls are very well thought out. Everything is modular, including the front panel, so it is very easy to work on. All connections are through the front panel, the case is sealed with finger stock, and nothing gets in except through the antenna connector. It is really remarkably RF tight.
N8FVJ Rating: 2017-03-19
Great Time Owned: 6 to 12 months.
Collins produced an ad for this receiver. They stated the R-648 was designed with many the 51J-4 design features. Unlike the 51j-4 the R-648 has a tunable RF front end with variable cores like the R-390 series. Using dual RF amplifier tubes and the tuned front-end it is unaffected by powerful shortwave stations and in band strong stations. Like the R-390 the R-648 may be the ultimate AM receiver.

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Earlier 5-star review posted by N8FVJ on 2017-03-18

The Collins R-648 receiver is a Mil Spec built design for the US Air Force in 1956 thru guessing 1960. It has a tunable front-end like the Collins R-390 & R-390A and weighs about 35 lbs.

The receiver is very quiet on the ham bands. 75 meter AM kind of just pops out of the low noise with a strong signal. I can hear most ham AM stations and this is a better receiver than the great performing National NC-183D. Having double conversion, there are no 'ghost' signals on the shortwave bands.

Controls are limited compared to the ham receivers of past. However, the receiver works so well controls such as crystal phasing, Q Multipliers, Noise Limiters, etc are not needed. This receiver has a full time noise limiter and it does not cause any distortion. The RF gain is a screwdriver adjustable control under a spring cover. It is located on the front panel and could be converted to a knob control.

The receivers only used a 28 volt dynamotor supplying 250 volts DC at 100ma. Converting to 120 volts AC power supply requires DC on the tube filaments due to many electrolytic capacitors in the filament circuit. 26 volts AC with convert to 27 volts DC with standard rectifiers and a CRC filter having 2 ohms resistance. 20,000uF per caps makes less than .05 volts AC ripple. B+ is a simple design not needed to be mentioned here.

If you have a chance to buy one, I would spend the $500 to $600. Having 17 tubes, I is a powerful receiver.