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Author Topic: Texas Star DX667V  (Read 10440 times)
W0QHT
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Posts: 7




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« on: June 14, 2011, 10:48:26 AM »

Hi, to all I have a question related to this amp, someone is selling me one of this amps but the guy dont know much about it and before I buy it I want to know if this amp is the high drive model or the standard model is there anything I should look for to find out if this is the high drive model or not. How can I tell if is one or the other?? any help will be appreciated, thank you
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N4ATS
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Posts: 807




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« Reply #1 on: June 14, 2011, 11:05:06 AM »

Its a typical CB Amplifier , High IMD, Zero filtering and just flat balls to the wall dirty RF output.... 667V stands for 600 watts output , 60 watts Drive (high) and the 7V stands for Variable...Great for channel 6....but NOT for a Licensed Amateur Radio Operator..
« Last Edit: June 15, 2011, 04:10:50 AM by N4ATS » Logged
AD6KA
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Posts: 2236




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« Reply #2 on: June 14, 2011, 02:48:13 PM »

Quote
any help will be appreciated, thank you
Your license, "W0QHT" expired three years ago, and then was cancelled one year ago.
Suggest you take care of that issue before you go amp shopping and getting on the air.
Ken,  AD6KA
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W8JI
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« Reply #3 on: June 14, 2011, 03:00:53 PM »

The weird world of CB and Ham meshing.
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WD8T
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Posts: 126




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« Reply #4 on: June 15, 2011, 06:56:16 AM »

The weird world of CB and Ham meshing.

   Lips sealed
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K9FON
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Posts: 1012




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« Reply #5 on: June 15, 2011, 10:59:35 AM »

CB junk thats filtering into our ham bands.. Guys, its never going to get better. Undecided Undecided
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KB1GTX
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Posts: 461




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« Reply #6 on: June 15, 2011, 11:20:36 AM »

What are you going to dive it with? hopefully not a  cb on 27 mhz!
The amp is actually built as well as most ham sets of the day including a bias supply and negative feed back making for a fairly clean imd as log as it's not over driven!
It does need a harmonic filter though.
Drive on that 2 stage amp is only a few watts pep for max clean output.
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W8JI
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« Reply #7 on: June 15, 2011, 02:47:48 PM »

What are you going to dive it with? hopefully not a  cb on 27 mhz!
The amp is actually built as well as most ham sets of the day including a bias supply and negative feed back making for a fairly clean imd as log as it's not over driven!
It does need a harmonic filter though.
Drive on that 2 stage amp is only a few watts pep for max clean output.


I honestly don't know where Hams come up with the stuff they do.

Here is a schematic:

http://www.cbtricks.com/Amp/txstar/dx667_dx667v/graphics/ts_dx667v_sch.pdf

You'll see that is the most half-arsed attempt at a bias circuit anyone would have.

First, the driver stage and PA stage share common bias on half of the output side, this puts (2) 10 ohm, one 2.7 ohm, and a 6.8 in parallel sources from a 25 ohm series to Vcc. That means we have a 1.4 ohm driven from a 25 ohms, so bias at zero mA base current (no drive) is 5.3% of supply, or .68 volts with 13 volts supply on one output side. This is UNregulated.

It has .5 amps quiescent current in the bias, so every 100 mA of base current from the driver and PA base currents summed will push the bias about .15 volts lower. The transistors are already just at or in cutoff with no drive, so with any base current they move to class C.

The other side of the PA has (2) ten ohm in parallel with 1.8 ohms, for a lower leg resistance of 1.32 ohms. That side has 5% of applied voltage for bias, with zero base current. With no drive it has .65 volts which will put the transistors in cutoff.

That side does not sum driver base current (from RF drive) into the load on the bias, but will still roll off bias at about .15 volts per 100 mA of base current.  So one side starts barely into class C, and by the time 150-200 watts is reached will be pretty deep into class C.

Apparently some of us thing transistors do not have base current, and that an unregulated bias source that is already just at or below cutoff is a good bias system.

That design clearly is to give the amp "RF AGC", which is typical for CB amplifiers. The more drive is applied, the deeper into class C the amp moves. This gives audio RF clipping, makes the amp less sensitive to drive power changes (because it is non-linear with built in automatic gain compression), and can make meters dance around on AM which puts CB'ers over the moon with joy.

A real bias system would have up around .75 volts bias, and be very stiff with varying base current. This system is clearly is just CB junk.

73 Tom


while the other half runs with more bias voltage!!!

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N4NYY
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« Reply #8 on: June 15, 2011, 03:15:07 PM »

Holy crap. I didn't know they actually published schematics for CB amps.
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KB1GTX
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Posts: 461




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« Reply #9 on: June 15, 2011, 06:17:13 PM »

That schamttic does not show the diode regulated bias supply that those amp use.
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W8JI
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« Reply #10 on: June 16, 2011, 05:57:00 AM »

That schamttic does not show the diode regulated bias supply that those amp use.

So what is the regulated bias system, and how do we know they did that right?

If they did do it right, how will someone buying one know if they are buying one with the "regulated" bias system or getting one without the working bias system?


This is the problem when we buy back-door things that are manufactured and sold illegally. We never know what it really is, because they are never under any pressure to meet any type of standard. If they bias it correctly, it will actually hurt the CB sales. CB'ers like to see meters swing around, and they do not normally have adjustable drive power available unless they also have an illegal radio.

So how do we blend all this illegal inconsistent stuff into the Ham bands without splattering up our Ham bands?
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W3LK
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Posts: 5644




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« Reply #11 on: June 16, 2011, 06:46:47 AM »

KB1GTX:

Stan, are you aware that your license expired over a month ago - 10 MAY 2011?
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
WD8T
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Posts: 126




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« Reply #12 on: June 16, 2011, 05:49:27 PM »

Ooopsie...W0QHT and KB1GTX better stay awy from those dirty CB amps and the PTT on their ham radio. Scuse me while I go pee in my pool. 
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AD6KA
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Posts: 2236




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« Reply #13 on: June 16, 2011, 07:53:58 PM »

Ooopsie...W0QHT and KB1GTX better stay away from those dirty CB amps and the PTT on their ham radio.

A thread about a CB amp started by a guy with a cancelled license, 
and the one poster defending the quality of said CB amp has an expired license.

What are the odds?
Coincidence?
Ken, AD6KA
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ZENKI
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Posts: 914




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« Reply #14 on: June 18, 2011, 02:14:50 AM »

CBérs showing hams how its done with their CB amps.  How did these  people even get their ham license when they dont even know that its wrong using class C amps like RM Italy, Palomar and Texas Star. The bands are full of these idiots. They even have no shame advertising the fact that they using these amps on QRZ.COM on their profile. The licensing system is failing the ham community when we its lets these poorly educated fools think that its okay to use these amps on the bands. I mean  there are so many nice cheap amps available from Ameritron why use these CB amps? I just dont get this stupid selfish attitude by these CB LID hams. Its so easy spotting these hams  using these amps with a SDR receiver, they have a very recognizable splatter/IMD signature. It so bad down on 10 meters that   you can hear splatter from stations that are S3 to S5, that is shocking! I guess 27mhz has arrived on the ham bands!
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