2SC2999 modification questioned

You sir are correct concerning magic receiver mods.

Now you can either ignore the folks who swear this stuff works or argue with them.

Lots of snake oil in radio land.

OK - I'll bite.

When the 858 chassis were around, there was no need for the 2999 mod. To use one would be a step backwards. Since the 8719 chassis was introduced, then it was found that the quality of parts chosen by the design and mfr had some room for improvement. That info is anecdotal; but it also passes scrutiny.

Having said that, it is no small wonder that someone using a cross reference chart for transistor replacement found that the 2999 just had better specs. But it was more than that. When the mfr chose to use the 1674, they chose an inferior grade of that device and bought them in wholesale lot. The tolerances of these parts were anything but consistent and no effort was made to pick and choose the better devices. Mass production took the front seat and the cost consideration took its toll for a consistent product.

So it is no small surprise that a better grade of transistor and one with better specs can reap some meager benefit. That depends entirely on the quality of the 1674 it is replacing. But one must also admit that any improvement in receive from the days of the 858 is still much better than a poke in the eye with a sharp stick. I have never said that it is a wonder drug nor is it likely to be national news. I would be leery of those who would claim such.

It will provide today's radio operator with an excuse to use his soldering iron and play radio. As some radios with the stock 1674 are poorer than others, it is no small surprise when one upgrades to a better quality part with cleaner gain. When used in conjunction with the Shottky diodes, AM performance can be markedly improved. Not all radios will see the same amount of change for the better. Some more; some less. But better than that stick in the eye.

The device that is taken out of the AM position when doing this mod is often put in the SSB receive device spot and improving it as well. Not a fantastic change; but still better than nothing. Putting a 2999 in that spot can be done, as it will improve SSB further. Been there; done that. Again, the variable of the stock part and the consistent quality of the replacement is the main factor.

Now, if this question was posed because of particular techs selling a multiple 2999 replacements, I have no comment. As I have never tried to go that far with this kind of mod. Such an evaluation is purely subjective to the end user. Speculation without any kind of personal experience or evidence is a fruitless endeavor. I can however say that all of the radios that I have done this mod with have seen mild to modest improvement. If you use and listen to the same radio day in and out; then these changes are apparent - not staggering. But appreciated - nonetheless.

Using the formula of substituting better devices throughout the entire radio can only yield better results. Some may argue that it is useless to consider and to execute. We may be talking about minor differences, but that is just not so. The level of inconsistencies between the same model of radio with a varied degree of part quality from a mfr that is interested in the bottom line profit vs cost - is a sure guarantee that the overall result will be better. Simple because there is less variation and the basic design can be maximized. That is the real argument here - IMO . . .

i dont think that its the increase in gain that people are drawn to when doing this mod, its the lower noise floor.

the typical 1674 has about a 4-6db noise spec.

the 2999 is shown to be 2.2 on the datasheet.

i dont really know how much change this actually makes in a radio, but that is why the mod has gotten so popular.

i actually think the schottky diodes make more of a difference than the 2999 does.

Justin, im sure we would all rather be using the MOSFET or GAASFET mod you and Bill used to offer, but we need a schematic so we can try it. hint hint...

LC

loosecannon said:

i actually think the schottky diodes make more of a difference than the 2999 does.

Click to expand...

Robb -

Excellent post. Absolutely correct.

LC -
You're right, almost all of the receive improvement comes from the diode swap and not from the 2999. In the 858 sets, the 2SC1730 is a far better device than the 2999.

- 399

2999 mod

I just got through doing this mod to my Galaxy 94HP yesterday, in this case I did a complete alignment to get the desired results, the mod worked well on the 94HP, did a side by side check before and after test against a Galaxy 98VHP an a General Lee which uses a 3600-15c board an is my best, in practice mobil receiver. Before the mod the GL was the low noise receiver that pulled in weak stations best, the 98VHP is used for a base, but it pulled in weak station quite good in a mobile. I use a NTE 107 instead of the 2999 in the 98VHP because don't need extra gain with base antenna. The 94HP pulled in all the station as the other radios did but with a lot more noise to go with it, hard on my old ears. After doing the mod an alignment and setting the the final gain in my mobile when the band is the quietest in the day, It worked out the GL is still the quietest receiver, but now the 94HP hears the weakest signals best and is quieter than the 98VHP in the mobile and has fuller robust audio than the 98VHP and thats saying something to me, I am very HAPPY with the results.............Oldtimer

loosecannon said:

i dont think that its the increase in gain that people are drawn to when doing this mod, its the lower noise floor.

the typical 1674 has about a 4-6db noise spec.

the 2999 is shown to be 2.2 on the datasheet.

i dont really know how much change this actually makes in a radio, but that is why the mod has gotten so popular.

i actually think the schottky diodes make more of a difference than the 2999 does.

Justin, im sure we would all rather be using the MOSFET or GAASFET mod you and Bill used to offer, but we need a schematic so we can try it. hint hint...

LC

Click to expand...

REAL WORLD it DOES help on very weak signals my GRANT LT went from .7UV to .4 UV for 10 db S/N on a IFR-1200S .... but is it worth moding every set no it is not ....

Great post Guys!!!!

Check this thread, Doc.

https://www.google.com/url?sa=t&rct...9YHgAg&usg=AFQjCNHzJw32dvWdRLIqOimVieVA0LoEIg

- 399

I saw this thread was started by Justin Depolis,I read on Google recently where he and his girlfriend were arrested in Cali,both crooks and scam artists,he was here as well.

techradioman said:

I saw this thread was started by Justin Depolis,I read on Google recently where he and his girlfriend were arrested in Cali,both crooks and scam artists,he was here as well.

Click to expand...

LOL yea that name is a bad blast from the past.

Justin is extremely knowledgeable about radio electronics and theory. It's a shame that he can't stay on the right side of the law.

I have a radio in my work van. A stock uniden pro 510-XL this radio with a Wilson 1000 has a great transmitted signal. and distance with a stock mic. I have had the report from several people I can trust.But the receive when I turn up the volume brings in more noise at the same time.. My question is I wanted to up grade the radio and was going to buy new amd AM olny unless AM/SSB radio would have a much better receive. What radios have the best stock receive or with a inexpensive mod would be the best. Cobra,Galaxy,connex, I would prefer to spend 100.00 for a cobra 29 than 200.+ for a General Lee if it isn't worth the extra money olny for the channels and power etc. It's the quality of the receive That I am looking at. Thanks!