Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Converting 10 meter brick to 6 m  (Read 12002 times)
KG4PFO
Member

Posts: 174




Ignore
« on: June 09, 2003, 11:09:41 PM »

Shouldnt I be able to convert a 4 pill 10 meter amp (4-sd-1446 pill Good for 6)by simply changing the input transformers to load 6 meters???
Anyone attempted this???
Knowledge wanted.....

Thanks
KG4PFO
Logged
WB2WIK
Member

Posts: 21837




Ignore
« Reply #1 on: June 10, 2003, 01:31:50 PM »

Try it!

You need to change more than the "input transformers," as both input and output are critically tuned circuits with power combiners, and none are wideband so they must be replaced with suitable circuits for 50 MHz.

You might need to tweak bypass capacitors and decoupling networks to optimize them for six meters, also, as 28 MHz decoupling is often ineffective at double the frequency and could cause stability problems.

Still, a very worthwhile experiment.

WB2WIK/6
Logged
W5CEU
Member

Posts: 4




Ignore
« Reply #2 on: June 18, 2003, 12:05:52 AM »

I did it! They dont like it though..... 90% of the transistors cut off at 30Mhz and it runs alittle warm also..(look up the spec's at RF parts.com "MRF-455" etc.) I changed the transformer turns and a RF choke and tweeked the variable caps a bit.I get about half the rated power It still wakes up my little MFJ! ,most CB type amps are way over rated any how.I'd say use it for 10m and find a old sweep tube amp to mod.73's
Logged
N4GI
Member

Posts: 56


WWW

Ignore
« Reply #3 on: June 18, 2003, 11:17:23 AM »

Don't do it.  Those cheap "10meter" CB amps are nothing more than non-FCC-approved-dirty-hash-boxes spewing garbage about the airwaves.  

It's bad enough they are used to trash 10meters, 6meters can surely do without them - help keep the ham bands clean.

73,
Blake N4GI  
Logged
KG4PFO
Member

Posts: 174




Ignore
« Reply #4 on: July 07, 2003, 08:12:37 PM »

It wont spew emissions if you run filters, that would be the smart "and legal" thing to do.

KG4PFO
Logged
N6OTQ
Member

Posts: 6




Ignore
« Reply #5 on: July 11, 2003, 10:56:27 AM »

The SD1446 is rated to 50 MHz.  Please see
   < http://us.st.com/stonline/books/ascii/docs/2805.htm >

and disregard the previous "30 MHz cutoff" remark.  In general, RF transistors are specified with a cutoff frequency by the manufacturer because they begin to lose gain and exhibit other undesired effects like parasitic oscillation and unpredictable internal filtering effects based on stray inductance and capacitance of the internal structures.

The input and output transformers that worked from 80 to 10 meters probably will give you another half-octave of bandwidth, but there are capacitors on the input and output of those transformers that need to be reduced in value.  These capacitors serve to minimize the gain variance of the amp over frequency -- in a general sense, for SS amps, gain and frequency are inversely related.  A conversion should be simple and effective.  The trade off is that the lower frequency capability of the amp -- 80 meters -- will be lost.

I urge you NOT to just hook the amp to a 6M exciter to "see what happens" -- it might work, but it might also blow up.  You'd be much better off to attempt a modification, or trade the amp, or sell it and buy a dedicated 6M amp.  

None of us here have any illusions about what a "10 meter 4-pill brick" amplifier can be used for.  I hope I speak for everybody here when I express my personal feelings that the amplifier be kept in amateur service and used only in the ham bands, rather than selling it to someone who might misuse it.  Our best course of action is to convert CB equipment AND operators to legal radios and law-abiding ham radio operators.

Jim N6OTQ

PS -- the SD1446 is rated at 183 W max dissipation per device, and spec-ed at 55% efficiency.  So if this were used as a "disposable" amplifier, it could deliver somewhere around 800 watts in high-duty-cycle SSB in Class C.  We all know what that service is in the real world.

If you are clueless, it'll swing 1200+ on a Dosy.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!