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TINMAN AMP uses HG 2SC2879
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HG MRF477 Feedback From USA User
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HG MRF477 Feedback From USA User
 
    
Luis Rivera

zccs@email.com

I am an amateur operator and radio technican Im not repairing radios anymore for business but just for me and friends.

Taking advantage of the new solar cycle #24 the 10 meter ham radio band is wide open around the world and meny radio operators are taking their 10 meters out of the closet. The best 10 meter radios of all times is the Uniden HR-2510 (other versions includes HR-2600,HR-2830 & LINCOLN)(Many of them needs repairs and new rf output transistors after 20 years of existence.
One of the reasons that this radio was discontinued at the end of 1989 was that Motorola stop the production of the RF final transistor MRF477. Now the MRF477 is very expensive and hard to find. Many “subtitutes” out there but they don’t work and even can blow up and damage the radio.

After a long search I found the HG MRF477 transistor that work extraordinary well on the HR radios (Not tested yet on the Emperor TS-5010 10 meter radio).  Like any new Moto MRF477 installed retune the final rf section  to get the best output power is recommended, not a hard job.

HG MRF477 Installation:

Installation was a matter of removing the old not working MRF477  and installing the new HG MRF477 (Im sure that the installation of the HG MRF477 more than a fix is and update). Don’t forget to add some silicon compound to help heat transfer to the radio cooler frame.

TX output section tune:

To get the best power possible the AM power variable resistor (VR103) need to be adjusted , for SSB adjust VR104.The final Bias adjustment need to be increased from 5 to 10mA.

Equipments used to perform off air test:

Dosy peak meter, 50ohm 100W dummy load & Iota DLS-75 power supply.

Power output SSB 35-40W peak (Very stable)

Power output on AM/FM was set to 15W dead carrier and up to 35W aprox of peak power (Very stable)(After all test the AM/FM carrier level was re-adjusted to 10W to keep radio factory specs).

Power across the entire 10 meter band is almost the same with minimal diference. Power on 26Mhz frequency is 3-5W less (same as original moto  – remember the chassis was factory tunned for 28Mhz to 29Mhz…. this is a 10 meter radio not a CB radio)

Current drain about 7A

On air test reports:

Equipments used to perform on aire test:

Dosy peak meter,  A99 antenna tuned for 10 meter band & Iota DLS-75 power supply.

After many days doing dx on 10 meters I continue to get clear audio reports, stable rf power on all modes and the best of all is the temperature at very low levels after long periods of full ssb power, not possible with the original Moto part that fail very easy because it get hot after a few minutes of TX

Conclusion:

Great transistor!!! I can recommend this item to any one that want to update or fix the HR 10 meter radio family. Hope to see small RF amplifiers using this transistors. Keep doing a great job HG Semi !!!

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