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Reviews For: Collins 51J-4

Category: Receivers: non-amateur adaptable for ham use

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Review Summary For : Collins 51J-4
Reviews: 3MSRP: unknown
Description:
General coverage 550kHz to 30 MHZ tube type receiver. Features mechanical filters for better selectivity. 19 Tubes. Weight 41 lbs.
Product is not in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0035
KM1H Rating: 2021-09-22
A sure keeper Time Owned: more than 12 months.
Ive had mine for 35 years and havent had to replace anything but one of the BCB oscillator crystals. I'll probably do a recap and some tube swaps this winter (to take advantage of the new Solar Cycle) if the caps test leaky on a rebuilt 1941 Sprague Model 16.

It is mostly used DXing on the BCB, ham AM, and a few of the HF SW bands that arent polluted with thumpers begging for money

Carl
Ham since 1955
National Radio 1963-69
G4GZG Rating: 2021-02-25
Great old Collins receiver Time Owned: 0 to 3 months.
I acquired my 51J-4 quite recently.Being in the UK they aren't as common as in the US as our Racal RA17/RA117 is more ubiquitous. I have both and the 51J-4 has the edge on the Racal. Mine needed a slight realignment as was a bit deaf but once done performs really well on Ham bands and SWBC. I have three ex commercial receivers and honestly rate them in terms of ease of use, sensitivity and selectivity as :
1. Eddystone EC958/1 - ( 1978 and solid state so a bit unfair). More sensitive and selectivity is sharper. Ease of use better.
2. Collins 51J-4 - Slightly less sensitive and a bit noisier than the Eddystone. Seelectivity is good and performs really well on AM.
3. Racal RA117 - About on a par with the Collins for sensitivity most of the time, selectivity not as good below 1.2KHz, Ease of use not as good due to constant need to retune the front end.

Overall the 51J-4 is an excellent receiver for todays use. Could do with better bandspread but this is typical of all old non amateur radios before the later solid state ones. I intend to take a proper look at it over the next few months and possibly replace some of the aged components.
N8FVJ Rating: 2020-11-29
Very serious receiver Time Owned: 3 to 6 months.
The Collins 51J-4 receiver is a very good receiver and especially so for Ham AM use. The 51J-4 is similar to the 51J-3 or R-388 with the addition of three mechanical filters. The bandwidth is 6, 3.1 and 1 kHz. Some radios may had 1 or 2 filters removed due to high market prices of used mechanical filters. The 51J-4 uses a 500 kHz IF, not the more common 455 kHz. I found 500kHz filters in the $50 to $100 range.
The 51J-4 is full featured including a good functioning Noise limiter and five (5) position variable crystal filter. AVC works well. The receiver is sensitive with a 6AK5 RF amplifier. Although the later and more common 6BZ6 is a little higher gain, it is not needed in the 51J-4. It receives weak signals very well on 10 meters. The radio has about 300 Hz drift in first minute and settles down to about zero drift in 5 minutes. The frequency dial is so accurate using the built in calibrator you do not need a frequency counter.
The is a very easy receiver to rebuild. The only issues are the capacitors. It has a huge number of .01uF at 36 installed. However, the capacitors are tubuliar ceramic and measure above 50 meg ohms, thus replacement is not required. It has seven .1 uF in bathtub style cans. These are very easy to replace being out in the open. Two 20 uF and two 8 uF are also in bathtub cans. It also has a dual can type plug in electrolytic capacitor. Heyseed sells new replacements. That is it! I replaced the capacitors in less than an hour. Watch the polatity of the two 20uF. Schematic is wrong, the capacitors have the positive (+) to ground.
On Ham AM nets there is rarely a signal I can not hear. The Hallicrafters SX-71 that is a good receiver is not as good as this 51J-4.
Prices are not inexpensive like any Collins receiver. Expect to p[ay $500 to $800 for a good cosmetic operating radio. Frankly, this is the last receiver you will ever need.