ICOM AG-25, 2M Mast Mounted Preamplifier
Hello The Net:
I recently got in Bob's (W7LRD) preamp for testing, with the following results:
144 MHz G = 27 dB NF = 1.3 dB 145 G = 27 dB NF = 1.1 dB 146 G = 27 dB NF = 0.9 dB 147 G = 26 dB NF = 0.8 dB 148 G = 25 dB NF = 0.9 dB
Performance is better than I expected, but lotsa gain.
DC voltage applied was 14 Vdc and lowered to 8 Vdc with no change in NF, but a 1 dB reduction in gain. DC current was ~200 milliamperes at 14 V and 117 milliamperes at 8.0 volts applied. Below 8 Vdc, the gain decreases rapidly and the NF increases. I like the wide operating voltage range.
The RF connectors are UHF type. There is a larger screw with a plastic washer underneath, but upon removal there is NO adjustment underneath for neither pass band tuning or gain reduction.
Reportedly there is a variable capacitor inside to allow tuning, but nothing externally accessible.
Has anyone found a adjustment for gain ?
Only choice I can think of is to reduce the RF gain on the transceiver when the preamp is menu enabled.
If an attenuator is put in line, the TX power would also be attenuated. We do not want to just throw away RF power in an attenuator
Stan, W1LE Cape Cod FN41sr Cape Cod
ZZZZz
The preamp is the Icom AG-25, which in the past has had questionable or unknown specs. Thanks to Stan now we know.
73 Bob W7LRD
----- Original Message ----- From: "W1LE Stan" stanw1le@verizon.net To: amsat-bb@amsat.org Sent: Wednesday, March 24, 2010 10:23:59 AM GMT -08:00 US/Canada Pacific Subject: [amsat-bb] ICOM AG-25, 2M Mast Mounted Preamplifier
Hello The Net:
I recently got in Bob's (W7LRD) preamp for testing, with the following results:
144 MHz G = 27 dB NF = 1.3 dB 145 G = 27 dB NF = 1.1 dB 146 G = 27 dB NF = 0.9 dB 147 G = 26 dB NF = 0.8 dB 148 G = 25 dB NF = 0.9 dB
Performance is better than I expected, but lotsa gain.
DC voltage applied was 14 Vdc and lowered to 8 Vdc with no change in NF, but a 1 dB reduction in gain. DC current was ~200 milliamperes at 14 V and 117 milliamperes at 8.0 volts applied. Below 8 Vdc, the gain decreases rapidly and the NF increases. I like the wide operating voltage range.
The RF connectors are UHF type. There is a larger screw with a plastic washer underneath, but upon removal there is NO adjustment underneath for neither pass band tuning or gain reduction.
Reportedly there is a variable capacitor inside to allow tuning, but nothing externally accessible.
Has anyone found a adjustment for gain ?
Only choice I can think of is to reduce the RF gain on the transceiver when the preamp is menu enabled.
If an attenuator is put in line, the TX power would also be attenuated. We do not want to just throw away RF power in an attenuator
Stan, W1LE Cape Cod FN41sr Cape Cod
ZZZZz _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (2)
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Bob- W7LRD -
Stan, W1LE