As many of you know there are a few ways to boost the incoming signal, generally this is done with a pre-amp style device; the drawback to a preamp is that it also boosts all other noises as well. It works the same as turning up the volume on your radio, as you can tell it does not help much if at all. What can you do to help? Well by swapping a few parts for upgraded parts you can make your radio more sensitive by boosting the incoming signal and helping to make the radio quieter on receive. The best part is that sense we will be working with the first IF stage of the radio all the garbage that would normally be boosted with a pre-amp will be filtered out so only the other radios carrier will be boosted. We will also help out the noise blanker section of the radio for quieter operation. This will not change the signal you receive on your meter but it will make a 3 s-unit signal as loud as a 4.5 s-unit signal. It also does not make your radio more prone to being overdriven up close. The swap is relatively quick, taking anywhere between 10 minutes for the experienced to 40 minutes to the first timer.
Today I will be using a Uniden Grant XL but the same applies to the Grant LT, Cobra 148 GTL, Uniden Washington, Cobra 2000 GTL, General Sherman, Texas Ranger 296, and countless other clones.
solder sucker, or c0pper braid
small side cutters
right angle pic (makes removing small parts easier)
#2 phillips screw driver
Parts needed - less than $15
1- 2sc2999 High Gain, Low Noise Transistor ( or nte107**)
4- 1N6263 Schottky Barrier Diodes (or nte583, ecg583, sk9975)
1- Transistor removed from the TR-14 position
You can begin by removing both the top and bottom case half?s, There is a total of 12 screws that need to be removed (4 per side, 1 on top and bottom, and 2 in the rear). I find the speaker easier to unsolder rather than clip the nylon zip ties and unplug from the main board. If you chose to unsolder the wires at the speaker remember that the White wire is the Positive (+) lead.
Take a look at the component side of the radio and find the positions outlined below. They are TR-14*, TR-19*, D1, D2, D21, And D22. These areas are where we will be working. Also take note of the orientation of the transistors (TR?s) and note that the flat side faces the rear of the radio, It is important that the new parts be installed the same way, The same holds true for the Diodes (D?s) as the stripe must be facing the correct side on the new diodes.
I like to start with the transistor at position TR-14, this is the Am Detector. You need to unsolder this from the backside of the board; it?s easy to find its location on the rear by holding the radio up to a bright light and using a pen to mark one of the legs. Make sure it?s a pen and not a pencil. Once you have the Transistor lose, you can place it aside as you will be using it again in a second. Place the new 2sc2999 transistor in the TR-14 position with the flat side facing the rear of the radio. Flip the radio over and solder each leg. Heat the joint for 2-3 seconds before applying solder. A good joint is shiny joint not dull and grey. If it is you need to heat the joint longer.
Move over to the Transistor at TR-19 and remove it. Take the Transistor you removed from the TR-14 position and solder it in place, Again the flat side will face the rear of the radio. This is the ssb detector.
You can now replace the diodes at D1, D2, D21, and D22 with the new 1N6263 diodes. These are low noise diodes that help quiet the natural hiss of the radio. The bands on the D1 and D21 diodes will face towards the mic connector, the bands on the D2 and D22 diodes will face away from the mic connector.
you may want to have the recieve section of your radio aligned, i have found that most radios will not need one if the radio has been aligned before.
*early model radios will be marked with a Q instead of a TR, they are the same component.
**the nte107 can be either hit or miss, when nte bins there parts they have a few transistors that cross over to the nte107 part (including the stock piece) so there is a very good chance you will not be receiving an upgraded part. The 2sc2999 however is an upgraded part and you should find one before using the nte107 if possible.
Galaxy DX 33, 44, 55, 66, 73, 77, 88, 99, 11b, Pluto, Super Galaxy, Galaxy II, Saturn, SSB, Melaka, RCI2980, Eagle 2000, Connex 3300 (all), Superstar 3600, 3900 (all), Osaka 3900, General Lee, Voyager VR9000, Alan 87, Nortstar Galaxy clones and other radios that use the EPT-3600 series Main Board.
TR-18 (Q), D1, D2, D34, D35
RCI-2950 & 2970 (non dx) Mirage 2950, Sommerkamp 2000, Galaxy Saturn Turbo, Galaxy DX 22B, Galaxy DX 2527, RCI-2990, Eagle 5000, And other radios that use the EPT-2950 series Main Board.
I am not trying to run you mod down I am just pointing out it is very little to be gained from such a mod.
You need to look at this for a manufacturer point of view, if they could make improvement to there radio they would, it sales more units and that is the name of the game, it not to do with cost has as some people may think one transistor is the same cost as the current one when you are buying in quantity.
Rick (Euro Radio Co).
Or a parts list/diagram.
Fyi, to all wondering why I want to put it back, its because it really just makes the radio act like it has a pre-amp in line. The actual noise ratio is just the same. The part that really makes me not like it is the fact that the S meters range is ruined. Basically everyone hits me S9, even if its weak or strong. I do lots of tracking and can't use the S meter like a normal radio. RF gain down, same problem.
I have General Lee, which is the same as a Galaxy radio. I want to put all the components used for this mod back to stock.Rick wrote:What radio are you trying to put back to stock?
What is the PCB number?
In regards to re-aligning the s meter, it still doesn't work. If you set s9 = 50uV, it won't be correct for S5 ( a different uV level, not sure what it is at this time, but you get my point).
I have some times tested 10 or so transistors with the curve tracer before I have found what I am look for, and even when you have found the right one it not just a case swapping the transistor, you also need to do a full re-alignment using a RF signal generator and SINAD meter.
Most DIY types do not have the equipment to do the job in the first place that why they get bad results and that why people like me charge a good price to do the job.
To improve the RX performance on the Adams, change the following TR6/7 to 2SC2999, C32 to 6pF, TR15 to 2SC1675 one for TR6 or 7 will do, D10/11/15/16 to 2N6263.
If you change the above, you will need to do a full re-alignment using a RF signal generator and SINAD meter.
You should be able on SSB to get 0.28uV for 10db S/N, and on AM it should be about 0.45uV for 10db S/N.
This chassis is not very broadband so you will only get the above sensitivity over about 60 channels (E.G 30 channels each side from the channel you do your alignment from).
http://www.radio-electronics.com/info/r ... /sinad.php
if in the uk yellow pages stewart of reading for test gear.
You will need to reorient the NTE23 transistor pins to work.I uses a piece of a #24 wire plastic cover to isolate the pins.With the flat side of the transistor facing to you and leads pointing down.
I am talking about the NTE107 for a example only,because the first IF transistor in the CB radios has the same pinout as the NTE107.And this includes the 2SC1674,2SC1730,Etc,Etc.
I have done this mod in The Uniden Washington with the MB8719 PLL,the Cobra 148GTL,the Cobra 139XLR and many other radios in the first IF transistor with great results,but you have to readjust the RX meter pot.
I used the NTE 107 and the four NTE 583 Schottky diodes. I didn't have to do a front end alignment.
I have an filed expedient antenna that I use every now and then to check that ever thing is in working order. its a small 3ft Fire stick mounted on a 3ft 1 1/2 EMT conduit a top a tripod with a ground rod. the whole set up stands a little more then 6ft off the ground. it has a good SWR.
I couldn't believe how far I was able to receive, and quiet. I am going take ever thing out of storage. set up my Shakespear Big Stick wiht the full wave Fire stick on the 60ft mast.
I have done this mod in The Uniden Washington with the MB8719 PLL,the Cobra 148GTL,the Cobra 139XLR and many other radios in the first IF transistor with great results,but you have to readjust the RX meter pot.[/quote]
I have a Cherokee CBS-1000, that I would like to install the Schottky Diode swap too... but don't know the locations the transistors or the diodes in this radio... ANY HELP ??
- Posts: 5
- Joined: Sunday 26th Jun 2011, 1:39
- First Name: Jim
- Location: Troy, New York
I've been testing this mod by including this mod with select operators I have worked for over the last couple of years. These CB and 10 meter radio operators can't stop telling me just how happy they are with their reception. And how quiet their radios now are with this upgrade.
One thing to add. The radios from the 1990's have less noise period.
I run 4' Francis antennas. 18ft of coax.