Does any one of you know the noise figure of both Collins R 390A or Collins 51j4 ?

[XE1ZLG]

I have searching on the web for any information regarding the noise figure of 2 Collins receivers .... Collins 51j4 and Collins R 390A... Does any one of you has this information ??

Thnks and 73....

Luis Gtz.

[K9STH]

The minimum sensitivity for 10 dB (S+N/N) on the R-390 series is 1 microvolt for CW and 5 microvolts for AM.

The minimum sensitivity for 10 dB (S+N/N) on the 51J-4 is 5 to 10 microvolts on the AM broadcast band and from 2 to 4 microvolts depending on the frequency between 1.5 MHz and 30.5 MHz. The manual doesn't differentiate between AM and CW.

The LDS/MDS for both receivers in the CW mode is considerably better generally being 0.1 microvolts or less. Remember, that the ambient band noise on HF is generally in excess of the minimum sensitivity figures for either receiver. I don't have a 51J-4, but I do have a 51J-2 and a military R-388 (51J-3). Both receivers have an LDS/MDS of well under 0.1 microvolts.

Glen, K9STH

[SM0AOM]

When measured by the 12 dB SINAD method using 30% AM modulation in a 6 kHz bandwidth,
both the R-390A and the 51J-4 have equivalent noise figures in the 7 to 12 dB range depending on frequency.

It may be possible to reduce the noise figure on certain frequencies to about 5 dB by careful alignment.

73/
Karl-Arne
SM0AOM

[XE1ZLG]

When measured by the 12 dB SINAD method using 30% AM modulation in a 6 kHz bandwidth,
both the R-390A and the 51J-4 have equivalent noise figures in the 7 to 12 dB range depending on frequency.

It may be possible to reduce the noise figure on certain frequencies to about 5 dB by careful alignment.

73/
Karl-Arne
SM0AOM

OK Karl..... it is the first time that some one tells me the noise figure of the 51J4 ....there is a user review in eham.net for the R 390A , that says this radio can get a 4 db noise figure when proper aligned ... this is similar to what you said.... One question ? Did you measure this values ???

Thnks and 73.........Luis Gtz.

[WB2WIK]

I never measured one but theoretically the 6AK5 can have a very low noise figure at HF. A Bell Labs journal reference http://www.alcatel-lucent.com/bstj/v...tj25-3-385.pdf states 2.4 dB was achieved with the 6AK5 at 30 MHz when they performed that analysis in 1946 (!)

[KA4DPO]

When measured by the 12 dB SINAD method using 30% AM modulation in a 6 kHz bandwidth,
both the R-390A and the 51J-4 have equivalent noise figures in the 7 to 12 dB range depending on frequency.

It may be possible to reduce the noise figure on certain frequencies to about 5 dB by careful alignment.

73/
Karl-Arne
SM0AOM

A 5db noise figure would be very good for an HF radio front end, 10db is certainly not bad. The total noise figure for the receiver is probably not published but as long as there is sufficient gain to overcome the atmospheric and thermal noise on HF it shouldn't matter. I never worried too much about front end noise figure until I got above 50 MHZ.

[XE1ZLG]

A 5db noise figure would be very good for an HF radio front end, 10db is certainly not bad. The total noise figure for the receiver is probably not published but as long as there is sufficient gain to overcome the atmospheric and thermal noise on HF it shouldn't matter. I never worried too much about front end noise figure until I got above 50 MHZ.

Noise figure between 5-12 dbs on R 390A sounds excellent...; of all radios I have ( Yaesu Ftx 5000 included ) the Collins 51J4 is the one that has less noise... may be in the future I will add a R 390A to my Shack !! Even the " premium " Rx 340 from tentec adss more noise to the final S/N ratio( Rx 340 ---NF 14 .. puiblished in www.dxtra.com )....None of the modern yausu, Icom or Kenwood transceivers put the noise figure in the specs ... I am sure they get bad number in the hole radio...

73 and nice week for all XE1ZLG