Subject: Radio Shack HTA-20 to 3 Meters ! From: L.D.Brewer Date: 1997/01/30 Message-Id: <5cr64h$d5g@lana.zippo.com> Newsgroups: alt.radio.pirate Someone posted a request for the mod to the HTA - 20 2 meter amp. Well ... here goes ! We purchased the test unit at Rat Shax for $99.95. Upon first check the unit would do about 30 watts on the 2-meter band. It uses a 2SC1946A device, which is the equiv. of the ECG 344. The maximum freq. of this device was listed as 175 MHz. The replacement cost of this device is $19.90 from the newest RF Parts Catalog. This device is rated for 6 watts drive, but nowhere near that was required to get the rated 30 Watts out !!! Now the MOD ! Remove L-106 ( choke ) from the board and discard. Add a 20 to 70 pF Compression trimmer cap to the board where L-106 was. Spread L-105 and L-104 dramatically. ( these could be replaced with a coil of one more turn, but what the heck, you don't wanna pull the circuit board outta there !! ) Carefully tune all trimmers begining with the input. Grab a cold one ! Yer done ! After careful tuning here are the wattage results : 1/2 watt in from a stock FRB PLL = 18 Watts out. 1 watt in from a stock Veronica PLL = 29 Watts out. Measurements taken on a Bird wattmeter. Voltage was set at 14.5 volts. The unit drew almost 8 amps during test. Test Freq = 100.10 MHz 2nd Harmonic via the spectrum anaylizer, using the Veronica -45 dB NOTE ! ! you need to remove the primary lead wires from the unit if you are going to run it 24/7. There was a 1 volt drop in the amp with just the little 18" or so lead provided. use a minimum of 12 Ga. ALSO ! ! Run a fan on this thing if you are going to run it 24/7 It gets hot quick If you don't want to do the mods, and tune ups, ship your un-opened unit to us. We will mod and tune it for you for $39.95. If you can't find one, we will sell you one for $139.95 US ready to go. ( less fan )