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Selecting power Fets for 500 KC transmitter
Greetings!!!
I plan on building a 500 KC transmitter, 200 watts output. I have never worked with power FETS before. What is the selection method used in determining which FET to use?? I see some great FETS cheap. Example: IRFP254 250 volt Vdss RDS on .14 Amps 32 amps Rise time : 51 NS Cost; 2.50 each The data sheet does not spec any freq's ( Ft) like bipolar transistors?? How do I select the right FET??? freq range Thanks!!! The 500 KC transmitter will run at 28 VDC |
Selecting power Fets for 500 KC transmitter
I can hardly imagine just about any device like this having an Ft so low
that it wouldn't work at 500 KHz. What ham band do we have at 500 KHz? wrote: Greetings!!! I plan on building a 500 KC transmitter, 200 watts output. I have never worked with power FETS before. What is the selection method used in determining which FET to use?? I see some great FETS cheap. Example: IRFP254 250 volt Vdss RDS on .14 Amps 32 amps Rise time : 51 NS Cost; 2.50 each The data sheet does not spec any freq's ( Ft) like bipolar transistors?? How do I select the right FET??? freq range Thanks!!! The 500 KC transmitter will run at 28 VDC -- Scott http://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version) |
Selecting power Fets for 500 KC transmitter
-- Scotthttp://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version)- Hide quoted text - - Show quoted text - There are Part 5 licenses recently issued for a 2 year duration 505 to 515 KC to WD2XSH for 20 watts ERP... I doubt that even 200 watts will get you there with any normal ham antenna... denny / k8do RV7 - even super SLOWER build.... |
Selecting power Fets for 500 KC transmitter
Scott wrote:
I can hardly imagine just about any device like this having an Ft so low that it wouldn't work at 500 KHz. What ham band do we have at 500 KHz? wrote: Greetings!!! I plan on building a 500 KC transmitter, 200 watts output. I have never worked with power FETS before. What is the selection method used in determining which FET to use?? I see some great FETS cheap. Example: IRFP254 250 volt Vdss RDS on .14 Amps 32 amps Rise time : 51 NS Cost; 2.50 each The data sheet does not spec any freq's ( Ft) like bipolar transistors?? How do I select the right FET??? freq range Thanks!!! The 500 KC transmitter will run at 28 VDC Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... |
Selecting power Fets for 500 KC transmitter
"ken scharf" wrote in message . .. Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... I hope you clued him in.. (re. 262 kHz...) Pete |
Selecting power Fets for 500 KC transmitter
It is a temporary authorization to specific hams or is it for something
completely different and it just happens to be a ham who asked the original question?? Scott N0EDV Denny wrote: -- Scotthttp://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version)- Hide quoted text - - Show quoted text - There are Part 5 licenses recently issued for a 2 year duration 505 to 515 KC to WD2XSH for 20 watts ERP... I doubt that even 200 watts will get you there with any normal ham antenna... denny / k8do RV7 - even super SLOWER build.... -- Scott http://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version) |
Selecting power Fets for 500 KC transmitter
LOL!! That might be more fun then using "the finger"
Scott ken scharf wrote: Scott wrote: I can hardly imagine just about any device like this having an Ft so low that it wouldn't work at 500 KHz. What ham band do we have at 500 KHz? wrote: Greetings!!! I plan on building a 500 KC transmitter, 200 watts output. I have never worked with power FETS before. What is the selection method used in determining which FET to use?? I see some great FETS cheap. Example: IRFP254 250 volt Vdss RDS on .14 Amps 32 amps Rise time : 51 NS Cost; 2.50 each The data sheet does not spec any freq's ( Ft) like bipolar transistors?? How do I select the right FET??? freq range Thanks!!! The 500 KC transmitter will run at 28 VDC Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... -- Scott http://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version) |
Selecting power Fets for 500 KC transmitter
ken scharf wrote:
Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... "This is God. You don't even want to know what I'm going to do to you for cutting that poor beloved gentleman off. Just don't make any long-term plans." -- Dec. 6 (Bloomberg) -- Government officials and activists flying to Bali, Indonesia, for the United Nations meeting on climate change will cause as much pollution as 20,000 cars in a year. |
Selecting power Fets for 500 KC transmitter
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Selecting power Fets for 500 KC transmitter
On Dec 28, 7:03*pm, Scott wrote:
It is a temporary authorization to specific hams or is it for something completely different and it just happens to be a ham who asked the original question?? Scott N0EDV Denny wrote: -- Scotthttp://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version)- Hide quoted text - - Show quoted text - There are Part 5 licenses recently issued for a 2 year duration 505 to 515 KC to WD2XSH for 20 watts ERP... I doubt that even 200 watts will get you there with any normal ham antenna... denny / k8do RV7 - even super SLOWER build.... -- Scotthttp://corbenflyer.tripod.com/ Gotta Fly or Gonna Die Building RV-4 (Super Slow Build Version)- Hide quoted text - - Show quoted text - It's temporary (for now) and there are 23 licensees authorized... DO a search on the 500 kc and the call and you should come up with it... denny |
Selecting power Fets for 500 KC transmitter
Uncle Peter wrote:
"ken scharf" wrote in message . .. Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... I hope you clued him in.. (re. 262 kHz...) Pete I'm not too sure, but I think that today's car radios DO use 455khz. I think they stopped using 262khz some years back when Detroit started having the radios made in China and got rid of the RF stages. But, back then I think Mitch knew better. He never did build that transmitter, too bad it would have been fun. |
Selecting power Fets for 500 KC transmitter
ken scharf ) writes:
Uncle Peter wrote: "ken scharf" wrote in message . .. Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... I hope you clued him in.. (re. 262 kHz...) Pete I'm not too sure, but I think that today's car radios DO use 455khz. I think they stopped using 262khz some years back when Detroit started having the radios made in China and got rid of the RF stages. Actually, most of them use 450KHz nowadays. The synthesizer ICs are designed for 450KHz, presumably because of some fact that makes it easier to design for that IF, such as it allows an existing common crystal or something. I can't think of any car radio I've opened up that had digital tuning and not a 450KHz IF. It's not so absolute in other types of radios, but it is still a common IF (which can be a real bother if you've got a shortwave receiver and thus can't improve selectivity with a good and relatively cheap used 455KHz mechanical filter). 262KHz IFs in car radios did pretty much disappear with the coming of ceramic filters. And no car radio is being made without ceramic filters. Though, I think I did see one car radio, it must have had analog tuning, that did have a 262KHz ceramic filter. Michael |
Selecting power Fets for 500 KC transmitter
Michael Black wrote:
ken scharf ) writes: Uncle Peter wrote: "ken scharf" wrote in message . .. Well a friend of mine once wanted to build a mobile transmitter for 455khz AM and 10.7mhz FM so he could tell the bozo in the car ahead of him where to go after he cut him off..... I hope you clued him in.. (re. 262 kHz...) Pete I'm not too sure, but I think that today's car radios DO use 455khz. I think they stopped using 262khz some years back when Detroit started having the radios made in China and got rid of the RF stages. Actually, most of them use 450KHz nowadays. The synthesizer ICs are designed for 450KHz, presumably because of some fact that makes it easier to design for that IF, such as it allows an existing common crystal or something. I can't think of any car radio I've opened up that had digital tuning and not a 450KHz IF. It's not so absolute in other types of radios, but it is still a common IF (which can be a real bother if you've got a shortwave receiver and thus can't improve selectivity with a good and relatively cheap used 455KHz mechanical filter). 262KHz IFs in car radios did pretty much disappear with the coming of ceramic filters. And no car radio is being made without ceramic filters. Though, I think I did see one car radio, it must have had analog tuning, that did have a 262KHz ceramic filter. Michael The choice of an IF frequency makes an interesting bit of radio history. The first BC superhets used IF's from 90khz to several hundred khz. Eventually 135khz, 150khz, and 175khz became "standard" (I remember seeing replacement IF cans with these frequency numbers in J W Miller's catalog.) These sets had an RF stage so were not bothered much by images with such a low IF. Later during the depression when radio manufacturers had to cut costs the RF stage went away (along with the power transformers) and the IF frequency was raised to 455 (+/- a few). Car radios needed more sensitivity and selectivity to handle fringe area reception so they retained RF stages and used a 262khz IF. |
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