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

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: HW 8 Modifications  (Read 3371 times)
KE7WAV
Member

Posts: 128




Ignore
« on: February 02, 2013, 10:42:17 PM »

I saw an ad some time ago for an HW 8 for sale and in the ad the op mentioned that the front end FET had been upgraded to an MPF 102, which increased its abilities to RX weak signals. Tonight on a whim I tried it and wow did that change the receiver! I don't have the HW 8 handbook... So what other mods can you all suggest to help me get more from my little QRP as its my main rig yet again.
Tnxs KE7WAV
Logged
W9GB
Member

Posts: 2650




Ignore
« Reply #1 on: February 03, 2013, 06:46:00 AM »

Stephen -

The substitution of a FET (such as MPF102) for a bipolar transistor in a receiver front-end was a common modification in 1970s.

Heathkit HW-8 : various Internet resources
http://home.frognet.net/~mcfadden/wd8rif/hw8.htm

Heathkit HW-8 Page
http://www.nostalgickitscentral.com/heath/mods/hw8/hw8.html

Heathkit HW-8 Assembly Manual
http://www.utm.edu/staff/leeb/hw8.pdf

IF you can obtain a copy of Mike Bryce's (WB8VGE) HW-8 Handbook, this is a compilation if the various modifications suggested for the Heathkit HW-8 QRP transceiver.

All four HW-8 Handbooks now on one CD! 
http://www.qrparci.org/toystore/thetoystore.htm
The first edition from 1985 by Fred Bonavita, W5QJM. 
The second through fourth ( 1986, 1991 and 2003 ) by Michael Bryce, WB8VGE.
Everything you ever wanted to know about the HW-7, 8, or 9 but were afraid to ask!
« Last Edit: February 03, 2013, 06:54:30 AM by W9GB » Logged
WB6BYU
Member

Posts: 13458




Ignore
« Reply #2 on: February 03, 2013, 08:42:34 AM »

The original front end device was an MPF105, which is pretty similar to an MPF102.  The only
difference is in pinchoff voltage.  However, there is a lot of part-to-part variation with the
early FETs, and the one in your rig might have been biased properly.  While some mods
recommended a dual-gate MOSFET such as the 40673, I put a 2N4416 in my HW-8 because
it didn't require any circuit changes and it works great.

Other common mods include RIT, improved tuning rate, internal SWR meter, an audio
transformer or replace audio output stage to drive low impedance headphones, full QSK,
and a fix for some motorboating due to inadequate reverse bias on the band switching
diodes.

All are documented in the Hotwater Handbook mentioned by W9GB, and you can
find a number of them on mods.dk
Logged
KE7WAV
Member

Posts: 128




Ignore
« Reply #3 on: February 03, 2013, 09:24:58 PM »

Dale what is mods.dk? Thanks for the info.  Greg, I saw the link above on where to order a copy of the hot water handbook and I may pinch some pennies and do that.  I am having fun checking out the links etc. You provided. Some ops have really decked out their little rigs! I like the freq-mite addition...that could be useful sometimes.
« Last Edit: February 03, 2013, 09:30:12 PM by KE7WAV » Logged
WB6BYU
Member

Posts: 13458




Ignore
« Reply #4 on: February 04, 2013, 08:38:29 AM »

Quote from: KE7WAV

Dale what is mods.dk?



http://www.mods.dk/
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!