QEX

board.

L5—20 turns #26 wire close wound on '/> inch plastic form. L6—23 turns #26 wire close wound on '/4 inch plastic form, tapped at 3 turns.

L21, L22, L23—3 turns #24 tinned wire formed on a #4-40 machine screw. L24, L25, L26—See Fig 3 (FL6).

3 GHz. A home-brew assembly using this diode indicates a receiver noise figure of about 15 dB—a bit disappointing; I was hoping for 10 dB or better. Another test was the addition of a Down East 13LNAH preamp. The typical noise figure was specified at 0.4 to 0.5 dB, and the measured gain was 15 dB. When using this preamp, the receiver noise power increased four fold at the 29 MHz IF output, indicating a mixer NF of 9 dB with an overall NF of 1.2 dB.

One drawback of this receiver is that its size makes it difficult to install at the antenna for cable-loss compensation. I plan to use the 13LNAH preamp at the antenna and a MGA86576 MMIC in front of the receiver to compensate for cable loss. (It has a gain of 23 dB with a 1.5 dB NF.) A 25 foot section of RG8/m (RG8 mini-foam) fitted with BNC connectors has measured 6 dB insertion loss. This makes the overall calculated NF 1.0 dB. The 0.5 dB loss is almost entirely due to the cable attenuation; the mixer loss is essentially eliminated by the high-gain MMIC. I'll connect the FL1 waveguide filter between the cable and the MMIC to minimize the possibility of high-level spurious signals entering the MMIC amplifier.

References

'Down East Microwave Inc. 954 Route 519, Frenchtown, NJ 08825; tel 908996-3584, fax 908-996-3702; http:\\ downeastmicrowave.com\ 2Noise/Com, E 49 Midland Ave, Paramus, NJ 07652; tel 201-261-8797, fax 201 -261 -8339.

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