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Texas Star on HF
- Thread starter dxhound
- Start date
You realize that the 'aside from filtering' is the entire issue, a fairly expensive one to address and one that will take a lot of time with a station monitor and other bench equipment?
An amplifier circuit is trivial. An RF amp that is tuned for a band and meets spurious emissions and is linear...non-trivial.
There's a reason why the SGC and Ameritron mobile amps are priced as they are.
To be fair, a year ago, I came here asking similar questions and spent a lot of time reading and learning to finally understand what is involved. Don't run CB amps on HF, they are dirty and people will be interfered with by your splatter. There are plenty of people out there now with spectrum displays on their rigs and they are glad to send in reports on dirty signals.
An amplifier circuit is trivial. An RF amp that is tuned for a band and meets spurious emissions and is linear...non-trivial.
There's a reason why the SGC and Ameritron mobile amps are priced as they are.
To be fair, a year ago, I came here asking similar questions and spent a lot of time reading and learning to finally understand what is involved. Don't run CB amps on HF, they are dirty and people will be interfered with by your splatter. There are plenty of people out there now with spectrum displays on their rigs and they are glad to send in reports on dirty signals.
I just asked a similar question on the Sweet Sixteen. The trigger for me was the difference in price between the TS Star and some of the Ham Amps I was running into... Not having my license yet, I wasn't sure what the difference was, but it was clear there was something else going on. It's funny, because on the CB side of the world, the Texas Star is considered one of the cleanest signals out there (AB1 vs Class C which makes up the majority of technology).
B
BOOTY MONSTER
Guest
texas star amps have no filtering . they are an ab biased amp . having ab biasing doesnt mean a amp is filtered . they are also no where near able to work from 160-10 meters . if you want an inexpensive amp to talk on ham bands get an ameritron and a ptt switch for am use .
http://www.ameritron.com/products.php?catid=2&type=price
http://www.ameritron.com/products.php?catid=2&type=price
didn't mean to imply the TS was filtered; only saying it was a cleaner signal than the class c that saturates the 11 meter market. I do get though that they lack the internal quality of something like the ameritron...
I think the 'catch' with that "cleanest on CB" is that it very well may be. But, that certainly does not mean that it's clean at all when compared to legitimate, commercially available amplifiers. Sort of like trying to pick up a dog t*rd by the clean end... you know?
- 'Doc
- 'Doc
HF rigs put out 100 watts PEP.
Only the larger texas stars will take that kind of input, such as the DX-1600.
Also, HF rigs are capable of keying the amp. This means you dont need the annoying SSB delay on an amp which can be keyed by the radio.
These amps, since they're AB biased, are clean if you dont overdrive them.
I think 100 watts PEP per 2879 pill is clean.
Ham HF amps have an ALC output, which only activates if the radio tries to overdrive the amp. The ALC from the amp tells the radio to back off the power. This prevents damage to the amp, and prevents the dirty signal caused by overdriving. Since the texas star doesnt have ALC output, the driving radio needs to be carefully set not to overdrive the amp.
With reasonable RF drive level from the radio, harmonics are also less of an issue.
HF ham bands were set up so they're mostly harmonically related.
If you're asking about using a texas star for HF mobile, i would say go for it. But if this is base-station, i would recommend against it, simply because tubes are cleaner and more efficient for that.
Only the larger texas stars will take that kind of input, such as the DX-1600.
Also, HF rigs are capable of keying the amp. This means you dont need the annoying SSB delay on an amp which can be keyed by the radio.
These amps, since they're AB biased, are clean if you dont overdrive them.
I think 100 watts PEP per 2879 pill is clean.
Ham HF amps have an ALC output, which only activates if the radio tries to overdrive the amp. The ALC from the amp tells the radio to back off the power. This prevents damage to the amp, and prevents the dirty signal caused by overdriving. Since the texas star doesnt have ALC output, the driving radio needs to be carefully set not to overdrive the amp.
With reasonable RF drive level from the radio, harmonics are also less of an issue.
HF ham bands were set up so they're mostly harmonically related.
If you're asking about using a texas star for HF mobile, i would say go for it. But if this is base-station, i would recommend against it, simply because tubes are cleaner and more efficient for that.
An amplifier can be Class AB and STILL splatter all over the place. Overdriving it with a dirty radio that's modulating 372% or better; modified radios that are missing a few critical parts...
It's impossible to state that, since your amplifier is a Class AB-biased unit, your signal is clean. Lots more needs to be looked at upstream from the amplifier, before you can make a statement like that.
It's impossible to state that, since your amplifier is a Class AB-biased unit, your signal is clean. Lots more needs to be looked at upstream from the amplifier, before you can make a statement like that.
HAHAHA,
wow what a topic to cause quite a discussion. Let me give you a little more info on what I plan on doing. I already have an HF amp and will use it always except I want to experiment and try something new with equipment I already have. I aquired a new in the box TS 500v for $200 and want to play with it. The reason Im not worried about harmonics is, I have what im guessing to be an old military band filter unit. it has 1.5-2mhz, 3-5mhz 6-8.5mhz 20-25mhz and 26-32mhz. its a rather robust unit and can handle upto 4kw input. So this is my solution for harmonics and spurious emissions. My main concern is will the amp be able to amplify a 1.8mhz signal and remain stable without osscillating or getting close to thermal run away? I will prob start off using my ft817 with 10 watts peak on both AM and ssb and depending on my results maybe use my 857 with 25 -40 watts drive ssb.
wow what a topic to cause quite a discussion. Let me give you a little more info on what I plan on doing. I already have an HF amp and will use it always except I want to experiment and try something new with equipment I already have. I aquired a new in the box TS 500v for $200 and want to play with it. The reason Im not worried about harmonics is, I have what im guessing to be an old military band filter unit. it has 1.5-2mhz, 3-5mhz 6-8.5mhz 20-25mhz and 26-32mhz. its a rather robust unit and can handle upto 4kw input. So this is my solution for harmonics and spurious emissions. My main concern is will the amp be able to amplify a 1.8mhz signal and remain stable without osscillating or getting close to thermal run away? I will prob start off using my ft817 with 10 watts peak on both AM and ssb and depending on my results maybe use my 857 with 25 -40 watts drive ssb.
dxhound,
I'm not aware of anyone using that amplifier on the lower HF bands. That doesn't mean it can't be done, just that I'm not aware of anyone using one.
If you want to try it, why not? I would recommend taking it easy to start with, and paying attention to what you might be told about the resulting signal.
All amplifying devices (transistors/tubes/whatever) are not 'comfortable' operating on all frequencies. Some don't care for the low freqs, some don't care for the higher stuff. That's also dependent on the circuit they are sitting in. Some circuits just aren't optimized except for particular segments of bands. (One reason for more complicated amplifiers that operate well at more than just one spot.)
A 'lumped' filter at the end of a transmitting string of things may work, but seldom work as well as a properly designed device with that 'lumped' filter spread out in the circuit at the sources of that stuff being filtered out. (Odd way of saying it, but it makes sense.)
Band-pass filters work great for stopping stuff out of a particular 'band' range. Don't do squat for stuff inside that 'band' range, and are not very good interference filters because of that when the unwanted signals are IN that band.
High-pass/low-pass filters let stuff through that are above/below the 'cut off' frequency of those filters. Still nothing to stop stuff that aren't above/below that 'cut-off' point.
If the unwanted signal originates in the pass-band the only half way sure way of getting rid of it is by eliminating it at the source (all them other parts in there instead of them being 'lumped' at the output). Sure, they can be reduced somewhat, but you can bet that some of them are still getting through.
If I sound like I'm trying to discourage you from using that amplifier, it's because I am. Nothing says you can't, and maybe you ought too to see what happens. I'm also saying that you shouldn't put a lot of 'faith' in it working well. But try it! Certainly wouldn't be the first time I've been wrong.
- 'Doc
(Tried one similar to that amplifier once. Mobile, no one could find me to complain. Fixed was a completely different story!
Had to quit using it, which turned out to not be that big'a deal.)
I'm not aware of anyone using that amplifier on the lower HF bands. That doesn't mean it can't be done, just that I'm not aware of anyone using one.
If you want to try it, why not? I would recommend taking it easy to start with, and paying attention to what you might be told about the resulting signal.
All amplifying devices (transistors/tubes/whatever) are not 'comfortable' operating on all frequencies. Some don't care for the low freqs, some don't care for the higher stuff. That's also dependent on the circuit they are sitting in. Some circuits just aren't optimized except for particular segments of bands. (One reason for more complicated amplifiers that operate well at more than just one spot.)
A 'lumped' filter at the end of a transmitting string of things may work, but seldom work as well as a properly designed device with that 'lumped' filter spread out in the circuit at the sources of that stuff being filtered out. (Odd way of saying it, but it makes sense.)
Band-pass filters work great for stopping stuff out of a particular 'band' range. Don't do squat for stuff inside that 'band' range, and are not very good interference filters because of that when the unwanted signals are IN that band.
High-pass/low-pass filters let stuff through that are above/below the 'cut off' frequency of those filters. Still nothing to stop stuff that aren't above/below that 'cut-off' point.
If the unwanted signal originates in the pass-band the only half way sure way of getting rid of it is by eliminating it at the source (all them other parts in there instead of them being 'lumped' at the output). Sure, they can be reduced somewhat, but you can bet that some of them are still getting through.
If I sound like I'm trying to discourage you from using that amplifier, it's because I am. Nothing says you can't, and maybe you ought too to see what happens. I'm also saying that you shouldn't put a lot of 'faith' in it working well. But try it! Certainly wouldn't be the first time I've been wrong.
- 'Doc
(Tried one similar to that amplifier once. Mobile, no one could find me to complain. Fixed was a completely different story!
Had to quit using it, which turned out to not be that big'a deal.)
DXHound, a few years ago when Justin was still doing radio work, we tried to modify one of those to do exactly what you're talking about. It didn't work. There were just too many components in the design of the whole circuit that worked just fine on 10 meters, but didn't work at all (or burned out) when you started dropping down to 40 meters and below. I seem to remember that even the buttons on the front of the amp were problematic. If I remember right (it's been a while) it wasn't real difficult to get it working down to 20 meters, though.
The Texas Star is able to run 10 meters without really tunning well as far as 28.3000 - 28.5000 Im not sure about into 12 meters but Im guessing with a good Tuner it would work. As far as the other bands without the propper band selector switching like my Palomar TX-5200 has along with filtering its not going to happen. here is some pics of the TX-5200 like I use once in awhile mine has 4/2290 transistors in it I really dont use it much and was going to sell it but I think a few of the guys I talk to on 10 meters and 2 meters would stick there foot so far in my @$$ my breath would smell like shoe polish. These amplifiers are built like they should be I have other amplifiers but as far as Ham bands I have a Yaesu 2100B and a Ameritron that plug right into the wall so thats what i use but those palomar TX 5200 are scarce thats why I should really keep mine and as said they have the Propper filtering and band switching thats needed for the other bands. If you look at the pics on the link I post you will see the band selector on the front. Heres the link http://home-and-garden.webshots.com/album/330350949BofVBd
I use mine on 40m all the time with my ft817. Drive it w a TS VMod. Works fantastic! Just had to put a small tuner between the amp and the radio to match the input tune. Bob's your uncle.
