Topics

knq7a bias current


Ronald Hering
 

Hi All,
Finally getting around to finishing my knq7, but ran into a problem.
 The idle current is around 40 ma but when PTT is keyed it jumps up to around 1400ma at the low end. Any ideas on where to start looking? All help will be greatly appreciated. Thanks, Ron.



Adam Rong
 

Ron,

Have you observed very hot parts during transmission? Besides the trimmer position, please check if you have properly installed the insulators for BD139/D882 and IRF510.

Thanks,
Adam

于 2017-10-21 23:28, rhering6938@... [CHINA_QRP] 写道:

 

Hi All,
Finally getting around to finishing my knq7, but ran into a problem.
 The idle current is around 40 ma but when PTT is keyed it jumps up to around 1400ma at the low end. Any ideas on where to start looking? All help will be greatly appreciated. Thanks, Ron.




Ronald Hering
 

I did some more checking and changed the 510, the gate voltage goes to 2.2 volts on keying and the drain drops to around 10 volts all other voltages arereal close to the chart.
--------------------------------------------

On Sat, 10/21/17, Adam Rong rongxh@gmail.com [CHINA_QRP] <CHINA_QRP@yahoogroups.com> wrote:

Subject: Re: [CHINA_QRP] knq7a bias current
To: CHINA_QRP@yahoogroups.com
Date: Saturday, October 21, 2017, 10:40 AM


 












Ron,



Have you observed very hot parts during transmission?
Besides the
trimmer position, please check if you have properly
installed the
insulators for BD139/D882 and IRF510.



Thanks,

Adam



于 2017-10-21 23:28, rhering6938@att.net
[CHINA_QRP] 写道:



 


Hi All,

Finally getting around to finishing my knq7,
but ran into
a problem.

 The idle current is around 40 ma but when
PTT is keyed it
jumps up to around 1400ma at the low end. Any
ideas on
where to start looking? All help will be
greatly
appreciated. Thanks, Ron.
























#yiv0969315839 #yiv0969315839 --
#yiv0969315839ygrp-mkp {
border:1px solid #d8d8d8;font-family:Arial;margin:10px
0;padding:0 10px;}

#yiv0969315839 #yiv0969315839ygrp-mkp hr {
border:1px solid #d8d8d8;}

#yiv0969315839 #yiv0969315839ygrp-mkp #yiv0969315839hd {
color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px
0;}

#yiv0969315839 #yiv0969315839ygrp-mkp #yiv0969315839ads {
margin-bottom:10px;}

#yiv0969315839 #yiv0969315839ygrp-mkp .yiv0969315839ad {
padding:0 0;}

#yiv0969315839 #yiv0969315839ygrp-mkp .yiv0969315839ad p {
margin:0;}

#yiv0969315839 #yiv0969315839ygrp-mkp .yiv0969315839ad a {
color:#0000ff;text-decoration:none;}
#yiv0969315839 #yiv0969315839ygrp-sponsor
#yiv0969315839ygrp-lc {
font-family:Arial;}

#yiv0969315839 #yiv0969315839ygrp-sponsor
#yiv0969315839ygrp-lc #yiv0969315839hd {
margin:10px
0px;font-weight:700;font-size:78%;line-height:122%;}

#yiv0969315839 #yiv0969315839ygrp-sponsor
#yiv0969315839ygrp-lc .yiv0969315839ad {
margin-bottom:10px;padding:0 0;}

#yiv0969315839 #yiv0969315839actions {
font-family:Verdana;font-size:11px;padding:10px 0;}

#yiv0969315839 #yiv0969315839activity {
background-color:#e0ecee;float:left;font-family:Verdana;font-size:10px;padding:10px;}

#yiv0969315839 #yiv0969315839activity span {
font-weight:700;}

#yiv0969315839 #yiv0969315839activity span:first-child {
text-transform:uppercase;}

#yiv0969315839 #yiv0969315839activity span a {
color:#5085b6;text-decoration:none;}

#yiv0969315839 #yiv0969315839activity span span {
color:#ff7900;}

#yiv0969315839 #yiv0969315839activity span
.yiv0969315839underline {
text-decoration:underline;}

#yiv0969315839 .yiv0969315839attach {
clear:both;display:table;font-family:Arial;font-size:12px;padding:10px
0;width:400px;}

#yiv0969315839 .yiv0969315839attach div a {
text-decoration:none;}

#yiv0969315839 .yiv0969315839attach img {
border:none;padding-right:5px;}

#yiv0969315839 .yiv0969315839attach label {
display:block;margin-bottom:5px;}

#yiv0969315839 .yiv0969315839attach label a {
text-decoration:none;}

#yiv0969315839 blockquote {
margin:0 0 0 4px;}

#yiv0969315839 .yiv0969315839bold {
font-family:Arial;font-size:13px;font-weight:700;}

#yiv0969315839 .yiv0969315839bold a {
text-decoration:none;}

#yiv0969315839 dd.yiv0969315839last p a {
font-family:Verdana;font-weight:700;}

#yiv0969315839 dd.yiv0969315839last p span {
margin-right:10px;font-family:Verdana;font-weight:700;}

#yiv0969315839 dd.yiv0969315839last p
span.yiv0969315839yshortcuts {
margin-right:0;}

#yiv0969315839 div.yiv0969315839attach-table div div a {
text-decoration:none;}

#yiv0969315839 div.yiv0969315839attach-table {
width:400px;}

#yiv0969315839 div.yiv0969315839file-title a, #yiv0969315839
div.yiv0969315839file-title a:active, #yiv0969315839
div.yiv0969315839file-title a:hover, #yiv0969315839
div.yiv0969315839file-title a:visited {
text-decoration:none;}

#yiv0969315839 div.yiv0969315839photo-title a,
#yiv0969315839 div.yiv0969315839photo-title a:active,
#yiv0969315839 div.yiv0969315839photo-title a:hover,
#yiv0969315839 div.yiv0969315839photo-title a:visited {
text-decoration:none;}

#yiv0969315839 div#yiv0969315839ygrp-mlmsg
#yiv0969315839ygrp-msg p a span.yiv0969315839yshortcuts {
font-family:Verdana;font-size:10px;font-weight:normal;}

#yiv0969315839 .yiv0969315839green {
color:#628c2a;}

#yiv0969315839 .yiv0969315839MsoNormal {
margin:0 0 0 0;}

#yiv0969315839 o {
font-size:0;}

#yiv0969315839 #yiv0969315839photos div {
float:left;width:72px;}

#yiv0969315839 #yiv0969315839photos div div {
border:1px solid
#666666;min-height:62px;overflow:hidden;width:62px;}

#yiv0969315839 #yiv0969315839photos div label {
color:#666666;font-size:10px;overflow:hidden;text-align:center;white-space:nowrap;width:64px;}

#yiv0969315839 #yiv0969315839reco-category {
font-size:77%;}

#yiv0969315839 #yiv0969315839reco-desc {
font-size:77%;}

#yiv0969315839 .yiv0969315839replbq {
margin:4px;}

#yiv0969315839 #yiv0969315839ygrp-actbar div a:first-child {
margin-right:2px;padding-right:5px;}

#yiv0969315839 #yiv0969315839ygrp-mlmsg {
font-size:13px;font-family:Arial, helvetica, clean,
sans-serif;}

#yiv0969315839 #yiv0969315839ygrp-mlmsg table {
font-size:inherit;font:100%;}

#yiv0969315839 #yiv0969315839ygrp-mlmsg select,
#yiv0969315839 input, #yiv0969315839 textarea {
font:99% Arial, Helvetica, clean, sans-serif;}

#yiv0969315839 #yiv0969315839ygrp-mlmsg pre, #yiv0969315839
code {
font:115% monospace;}

#yiv0969315839 #yiv0969315839ygrp-mlmsg * {
line-height:1.22em;}

#yiv0969315839 #yiv0969315839ygrp-mlmsg #yiv0969315839logo {
padding-bottom:10px;}


#yiv0969315839 #yiv0969315839ygrp-msg p a {
font-family:Verdana;}

#yiv0969315839 #yiv0969315839ygrp-msg
p#yiv0969315839attach-count span {
color:#1E66AE;font-weight:700;}

#yiv0969315839 #yiv0969315839ygrp-reco
#yiv0969315839reco-head {
color:#ff7900;font-weight:700;}

#yiv0969315839 #yiv0969315839ygrp-reco {
margin-bottom:20px;padding:0px;}

#yiv0969315839 #yiv0969315839ygrp-sponsor #yiv0969315839ov
li a {
font-size:130%;text-decoration:none;}

#yiv0969315839 #yiv0969315839ygrp-sponsor #yiv0969315839ov
li {
font-size:77%;list-style-type:square;padding:6px 0;}

#yiv0969315839 #yiv0969315839ygrp-sponsor #yiv0969315839ov
ul {
margin:0;padding:0 0 0 8px;}

#yiv0969315839 #yiv0969315839ygrp-text {
font-family:Georgia;}

#yiv0969315839 #yiv0969315839ygrp-text p {
margin:0 0 1em 0;}

#yiv0969315839 #yiv0969315839ygrp-text tt {
font-size:120%;}

#yiv0969315839 #yiv0969315839ygrp-vital ul li:last-child {
border-right:none !important;
}
#yiv0969315839


kb1gmx@...
 

The drain should be very near the power supply voltage if its dropping its either a 
problem with the meter going nuts from RF (They do that!) or your power supply 
is weak.

The gate voltage for the final will vary from device to device for a given drain 
current.  I've seen 2-3V typical across a lot of IRF510s (I use them for a lot of stuff).

Other reasons for increased drain on TX is, final is oscillating, or carrier leakage.
The latter can be due to an error around the NE602 (U3 on some schematics).
If the device is unbalanced due to a misplaced part of other short or leakage
it will emit carrier and that will show RF power (maybe milliwatts) output and 
increased drain.  Also if the carrier frequency adjustment is way off you may 
not be on the edge of the filter pass band and instead you can be inside the
passband.  That can also contribute excess carrier at output.

Just a few thoughts.

Allison