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Hello
The problem with IRF510 RF amplifiers failing seems to be a recurring one for those who
are not quite careful with antenna matching, bias level, and drive level.? As a way to start
looking into this situation I have performed some on-line searches to see how others are
working around this problem.
And there is much more out there to be Google searched and reviewed.
There are a number of potentially useful ideas contained in those articles and discussions,
but nothing that obviously applies directly to the problem of blowing IRF510 devices at only
a few watts of power if the antenna is mis-matched.? Mention of using small resistance values
in series with gate drive is interesting, as is use of pi-net attenuators between exciter and
RF PA gate...to help control impedance?? While we look upon the MOSFET internal capacitance
as being a problem, it is interesting that some designs add a capacitor on the drain side of
things, apparently to limit the upper frequency capability and reduce 'spikes'.? The discussion
on single-ended versus push-pull is interesting from a technical view, but did not introduce
anything obvious that could help.
I suppose we have to first determine just what the exact cause of IRF510 failure might be,
then use that as the basis for designing a suitable solution.
Arv? K7HKL
_._
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Here is another:
In the middle of the page, is this:
"I destroyed many IRF510 FETs during testing. In fact I blew a small hole in one and another into several pieces. It was quite a shock when the first one was destroyed because it made a loud noise like a rifle being fired. Once I got tired of replacing the FETs, I built a current sense circuit, which shuts off the bias once the amplifier draws more than about 3 amps from the PSU. I think this circuit is essential. You can build it into the Power Supply or into the Amplifier. I built it into the Amplifier because the power supply, which is also homemade, does not limit until 7 amps. With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short." There is a schematic for the current limiting circuit that is used.? This might be something to incorporate into the design.? It is only 7 more parts.
Marco - KG5PRT
On Thu, Jan 25, 2018 at 10:48 PM, Arv Evans <arvid.evans@...> wrote: Hello
The problem with IRF510 RF amplifiers failing seems to be a recurring one for those who
are not quite careful with antenna matching, bias level, and drive level.? As a way to start
looking into this situation I have performed some on-line searches to see how others are
working around this problem.
And there is much more out there to be Google searched and reviewed.
There are a number of potentially useful ideas contained in those articles and discussions,
but nothing that obviously applies directly to the problem of blowing IRF510 devices at only
a few watts of power if the antenna is mis-matched.? Mention of using small resistance values
in series with gate drive is interesting, as is use of pi-net attenuators between exciter and
RF PA gate...to help control impedance?? While we look upon the MOSFET internal capacitance
as being a problem, it is interesting that some designs add a capacitor on the drain side of
things, apparently to limit the upper frequency capability and reduce 'spikes'.? The discussion
on single-ended versus push-pull is interesting from a technical view, but did not introduce
anything obvious that could help.
I suppose we have to first determine just what the exact cause of IRF510 failure might be,
then use that as the basis for designing a suitable solution.
Arv? K7HKL
_._
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Marco - KG5PRT
That is very interesting indeed.? Implementing this current based bias control
should be easy and could be compact.?  from: If I understand this correctly... - Voltage drop across R1 forward biases T2 to ON state
This lights the LED.
- Voltage on the collector of T2 turns T1 OFF, removing supply voltage
to the 5V bias regulator in the RF PA circuit.
I was looking toward a similar control based on reflected power but the current
based approach is easier, as long as it works.? This adds another project to my
to-do list.
Thanks for the URL.
Arv? K7HKL
_._
On Thu, Jan 25, 2018 at 10:11 PM, M Garza <mgarza896@...> wrote: Here is another:
In the middle of the page, is this:
"I destroyed many IRF510 FETs during testing. In fact I blew a small hole in one and another into several pieces. It was quite a shock when the first one was destroyed because it made a loud noise like a rifle being fired. Once I got tired of replacing the FETs, I built a current sense circuit, which shuts off the bias once the amplifier draws more than about 3 amps from the PSU. I think this circuit is essential. You can build it into the Power Supply or into the Amplifier. I built it into the Amplifier because the power supply, which is also homemade, does not limit until 7 amps. With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short." There is a schematic for the current limiting circuit that is used.? This might be something to incorporate into the design.? It is only 7 more parts.
Marco - KG5PRT
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A suitable fast-blow fuse or polyswitch in the PA-PWR line into the board should be sufficient to protect the IRF510's from too much current. The polyswitch is like a fuse, except it resets once it cools down after you remove power. A thermal sensor on the IRF510 heatsink that at least turns on a front panel LED might be a good idea. This old post here from Allison is informative, well worth re-reading every few months: ? ?? /g/BITX20/message/22597As she says, lots of things can kill an IRF510, but the most common is heat if you have a good amp design. Powering at 28v for 55W from a push-pull pair, she didn't see trouble when driving improper antenna impedances. I'd think that if powered at 12v, and if they have a reasonable heatsink, and if you don't screw up? when fiddling with the gate bias pots at rv2 and rv3, or drop a screwdriver into the wrong spot, the IRF510's should not blow.? Even when driving a non-existent antenna, the RF voltages at the drains go up some without a load, but not drastically, T11 is just a 1:2 voltage transformer. Driving a 0 ohm antenna might be a bit worse since the currents will go up, but probably survivable. Jerry, KE7ER
On Thu, Jan 25, 2018 at 09:11 pm, M Garza wrote:
There is a schematic for the current limiting circuit that is used.? This might be something to incorporate into the design.? It is only 7 more parts.
?
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Jerry, I do not disagree, I have a fuse inline with both power lines.? When a fuse blows, you dont know if there has been damage or not. In my opinion, it would be better to prevent the situation from being able to happen.? This idea seems to have worked for the builder,? since he made specific mention of it.?
"With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short."
Marco - KG5PRT
On Thu, Jan 25, 2018 at 11:37 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: A suitable fast-blow fuse or polyswitch in the PA-PWR line into the board should be sufficient
to protect the IRF510's from too much current.
The polyswitch is like a fuse, except it resets once it cools down after you remove power.
A thermal sensor on the IRF510 heatsink that at least turns on a front panel LED might be a good idea.
This old post here from Allison is informative, well worth re-reading every few months:
? ??/g/BITX20/message/22597
As she says, lots of things can kill an IRF510, but the most common is heat if you have a good amp design.
Powering at 28v for 55W from a push-pull pair, she didn't see trouble when driving improper antenna impedances.
I'd think that if powered at 12v, and if they have a reasonable heatsink, and if you don't screw up?
when fiddling with the gate bias pots at rv2 and rv3, or drop a screwdriver into the wrong spot,
the IRF510's should not blow.? Even when driving a non-existent antenna, the RF voltages at the drains
go up some without a load, but not drastically, T11 is just a 1:2 voltage transformer.
Driving a 0 ohm antenna might be a bit worse since the currents will go up, but probably survivable.
Jerry, KE7ER
On Thu, Jan 25, 2018 at 09:11 pm, M Garza wrote:
There is a schematic for the current limiting circuit that is used.? This might be something to incorporate into the design.? It is only 7 more parts.
?
|
I was looking at the data sheet from Mitsubishi for their RD15HVF1 and in the electrical characteristic table on page two it says: ?? Parameter????????????????????????????????????? Conditions??????????????????? Limits Load VSWR tolerance????????????? Load VSWR=20, ... ??????????? no destroy ??????????????????????????????????????????????? VDD=15.2V, Po=15W If I am reading this correctly it looks like at over voltage and high power out it is expected to survive a VSWR of 20. with friend google I also found? /g/QRPLabs/message/13357Wouldn't it be better to change to a RD15HVF1 for high VSWR rather than add circuits, even if the RD15HVF1 did not yield substantially better uBitx power performance at higher frequencies? ??? Bob?? KD8CGH
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I decided to add a polyswitch to my uBitx. Since it can draw almost 2 amps I selected a 3 amp, 16 V model. When I got them I tested one and found that I could not trip it with my 5 amp lab bench supply. Reading the specifications (after purchase - duh) I see that it is speced to trip at 6 amps continuous current with a max time to trip of 5 seconds at 15 amps. I'm not sure that this would protect the finals. In contrast, a 3 amp fast blow glass cartridge fuse is speced to blow? in 5 seconds at 6 amps.
I got a glass fuse holder and a handful of 2, 2.5 and 3 amp fuses. I'll see if I can get by with 2 amps in normal operation.
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One other possibility to consider to protect against overcurrent situations is to use a current limiting power supply, or add a current limiter to an existing power supply or battery.
The current limiter circuit whose link is at this site:
<>
will go up to 2.2 amps, and includes a low-dropout voltage regulator that also provides reverse polarity protection.
There is a version, in a different package, of that same regulator chip that has an added "tracking" feature - being able to parallel multiple chips to increase the available current. Details are on the datasheet in the document.
Jim, N5IB
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The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
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Show quoted text
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote:
Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
On same site I found these, made for 30 MHz? RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know.
toggle quoted message
Show quoted text
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io < jgaffke@...> wrote: The RD15HVF1's should be operated at not much more than 12v. At 12v, the IRF510's would survive just fine with no antenna connected. That's an infinite VSWR. So not obvious that this is a solution to blown FET's. Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's, which makes RV2,RV3 not so touchy. And the RD15HF1's might be easier to drive at 30mhz. If you do swap them in, let us know how much power you get at 30mhz. Jerry, KE7ER On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote:
Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
?
On Friday, January 26, 2018 1:01 PM, James Lawrie <lawriejk@...> wrote:
On same site I found these, made for 30 MHz? RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know.
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io < jgaffke@...> wrote: The RD15HVF1's should be operated at not much more than 12v. At 12v, the IRF510's would survive just fine with no antenna connected. That's an infinite VSWR. So not obvious that this is a solution to blown FET's. Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's, which makes RV2,RV3 not so touchy. And the RD15HF1's might be easier to drive at 30mhz. If you do swap them in, let us know how much power you get at 30mhz. Jerry, KE7ER On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote:
Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
Interesting comments thus far regarding IRF510 failures.? - Power supply current limiting (2.5 to 3A) seems to work.
- Bias voltage shutdown on high current (3A) seems to work.
- Driver impedance to IRF510 gate should be quite "stiff".? Use a 50 ohm pad.
- Use small resistance (4.7 ohms) in series with each IRF510 gate lead.
- Keep IRF510 leads short.
- Impedance presented to the IRF510 drain should be 12.5 ohms.
RF output transformer should be 1:2 windings for 1:4 impedance transition.
Binocular core may work better...?
- Avoid the problem by using some other MOSFET.
- Use plastic fuses at 3A for self-healing action.
- Fuse rig power at 2 to 3A to avoid IRF510 failures.
Some of the on-line information also mentioned low level background noise being generated by MOSFET RF PA stages that remain powered during receive mode.? Possible solution here might be to add a MOSFET switch in the DC power lead going to the IRF510s so this power could be shut off during receive.
All good info.? Now how to keep within the original BITX objective of making rigs
that can be afforded by those with limited spare cash and still make them reliable
and inexpensive.? This solution(s) has potential for modification of existing
transceivers, and for future redesign of the similar units.? It also has application
for designing and adding homebuilt RF amplifiers for your BITX rig.
Arv? K7HKL
_._
On Fri, Jan 26, 2018 at 10:32 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote:
Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too. ?Oh, did I mention, they are both real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ?
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From: [email protected] [mailto:[email protected]] On Behalf Of James Lawrie
Sent: Friday, January 26, 2018 2:01 PM
To: [email protected]
Subject: Re: [BITX20] IRF510 amplifier failures? On same site I found these, made for 30 MHz?RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know. ?
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote: Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
Hello,
That’s why I bought 10 ea... for the uBitxs I’ll probably get the others rated at over 30 MHz. Always nice to stock up on useful parts. Out of all listed on there website what would you recommend for HF/VHF use?
toggle quoted message
Show quoted text
On Jan 26, 2018, at 19:56, K9HZ < bill@...> wrote: The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too. ?Oh, did I mention, they are both real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? ? On same site I found these, made for 30 MHz?RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know. ?
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote: Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
Good morning. I was thinking about the RD15HVF1 so that it would be easier for people who want to try 50MHz and perhaps 70MHs where available with suitable mods to the μbitx.
The RD16HHF1 appears to be? used in the Ukraine transverters as a PA in the 50MHz, 70MHz and 144 MHz transverters while the RD15HBF1 appears to be used in the 222MHz and 432MHz transverters.? I have the 50MHz and 70MHz transverters and they do work.
Two years ago I worked more than 40 stations on 70MHz (see my log on QRZ dot com) with a simple dipole at about 4M high on the roof fed with some 50 feet of RG58 coax. Last year I built a 5 element LFA Yagi for 70MHz but didn't have time to get on the air.? Lots of data at
Regards Lawrence
On Sat, Jan 27, 2018 at 3:41 AM, James Lawrie <lawriejk@...> wrote: Hello,
That’s why I bought 10 ea... for the uBitxs I’ll probably get the others rated at over 30 MHz. Always nice to stock up on useful parts. Out of all listed on there website what would you recommend for HF/VHF use? On Jan 26, 2018, at 19:56, K9HZ < bill@...> wrote: The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too.? Oh, did I mention, they are both real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? ? On same site I found these, made for 30 MHz?RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know. ?
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote: Wouldn't it be better to change to a RD15HVF1 for high VSWR
|
Yoiu can get this kit also on ebay, a short researcht fgave a big
variety in price from about 5 euros including shipping up to 30
Euros!
So be carefull!!!
Henning Weddig
DK5LV
Am 26.01.2018 um 19:21 schrieb Thomas
Sharka via Groups.Io:
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Show quoted text
?
On Friday,
January 26, 2018 1:01 PM, James Lawrie
<lawriejk@...> wrote:
On same site I found these, made for 30 MHz? RD16HHF1. Sooo I
bought 10 of them, plan to try in Bix40 first.
Data sheet even shows a reference amp design, and
they are 12 volt like the other one. If it works
I’ll let everyone know.
On Jan 26, 2018, at 11:32, Jerry Gaffke via
Groups.Io < jgaffke@...>
wrote:
The RD15HVF1's should be operated at not
much more than 12v.
At 12v, the IRF510's would survive just fine
with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to
blown FET's.
Though I do think the the Ids curves go up
more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at
30mhz.
If you do swap them in, let us know how much
power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH
wrote:
Wouldn't it be better to change to
a RD15HVF1 for high VSWR
|
I don’t think it’s so much a matter of if they will work or not.? Both will work fine at 50 MHz (and above actually)… the issue is that the RD15HVF1 is a little flatter across the spectrum and from that perspective easier to design around and match.? I use them all the time and they are very easy parts to make work.? A pair will easily put out 30 watts 1-54 MHz if the rest of the design is correct. ? I’ve been thinking about and have had requests for a nice linear amplifier for the uBITx and these parts are cheap enough to use for that purpose too.? I originally designed one using two RD70HVF1 parts but the cheapest I’ve found them is $18 each.? Not a show stopper but the little brothers are cheaper.? If The parts were under $15 in large quantity, it would be a no brainer.? The auto tuner must be finished first though.? Oh, did I mention, the RD series devices are real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Lawrence Galea
Sent: Saturday, January 27, 2018 3:34 AM
To: [email protected]
Subject: Re: [BITX20] IRF510 amplifier failures ? I was thinking about the RD15HVF1 so that it would be easier for people who want to try 50MHz and perhaps 70MHs where available with suitable mods to the μbitx. The RD16HHF1 appears to be? used in the Ukraine transverters as a PA in the 50MHz, 70MHz and 144 MHz transverters while the RD15HBF1 appears to be used in the 222MHz and 432MHz transverters.? I have the 50MHz and 70MHz transverters and they do work.
Two years ago I worked more than 40 stations on 70MHz (see my log on QRZ dot com) with a simple dipole at about 4M high on the roof fed with some 50 feet of RG58 coax. Last year I built a 5 element LFA Yagi for 70MHz but didn't have time to get on the air.? ? On Sat, Jan 27, 2018 at 3:41 AM, James Lawrie <lawriejk@...> wrote: Hello, That’s why I bought 10 ea... for the uBitxs I’ll probably get the others rated at over 30 MHz. Always nice to stock up on useful parts. Out of all listed on there website what would you recommend for HF/VHF use?
On Jan 26, 2018, at 19:56, K9HZ <bill@...> wrote:
The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too.? Oh, did I mention, they are both real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? ? On same site I found these, made for 30 MHz?RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know. ?
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote: Wouldn't it be better to change to a RD15HVF1 for high VSWR
?
|
So if they are " real RF transistors" probably worth the extra then ?
Phil - G7BZD
On Sat, Jan 27, 2018 at 1:36 PM, K9HZ <bill@...> wrote: I don’t think it’s so much a matter of if they will work or not.? Both will work fine at 50 MHz (and above actually)… the issue is that the RD15HVF1 is a little flatter across the spectrum and from that perspective easier to design around and match.? I use them all the time and they are very easy parts to make work.? A pair will easily put out 30 watts 1-54 MHz if the rest of the design is correct. ? I’ve been thinking about and have had requests for a nice linear amplifier for the uBITx and these parts are cheap enough to use for that purpose too.? I originally designed one using two RD70HVF1 parts but the cheapest I’ve found them is $18 each.? Not a show stopper but the little brothers are cheaper.? If The parts were under $15 in large quantity, it would be a no brainer.? The auto tuner must be finished first though.? Oh, did I mention, the RD series devices are real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? From: [email protected] [mailto:[email protected]] On Behalf Of Lawrence Galea
Sent: Saturday, January 27, 2018 3:34 AM ? I was thinking about the RD15HVF1 so that it would be easier for people who want to try 50MHz and perhaps 70MHs where available with suitable mods to the μbitx. The RD16HHF1 appears to be? used in the Ukraine transverters as a PA in the 50MHz, 70MHz and 144 MHz transverters while the RD15HBF1 appears to be used in the 222MHz and 432MHz transverters.? I have the 50MHz and 70MHz transverters and they do work.
Two years ago I worked more than 40 stations on 70MHz (see my log on QRZ dot com) with a simple dipole at about 4M high on the roof fed with some 50 feet of RG58 coax. Last year I built a 5 element LFA Yagi for 70MHz but didn't have time to get on the air.? ? On Sat, Jan 27, 2018 at 3:41 AM, James Lawrie <lawriejk@...> wrote: Hello, That’s why I bought 10 ea... for the uBitxs I’ll probably get the others rated at over 30 MHz. Always nice to stock up on useful parts. Out of all listed on there website what would you recommend for HF/VHF use?
On Jan 26, 2018, at 19:56, K9HZ <bill@...> wrote:
The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too.? Oh, did I mention, they are both real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? ? On same site I found these, made for 30 MHz?RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know. ?
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote: Wouldn't it be better to change to a RD15HVF1 for high VSWR
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Well it’s this way.? You can either spend a little more on the transistor (with the nice input characteristics) and design with minimal parts (e.g. one set of broad band impedance matching transformers and bias network) to work over a large frequency range (1-54 MHz)…. Or you use a cheap motor switch like the 510 and live with the gain roll-off from mismatch (large del C / del Freq) with a fixed set of broad band I/O transformers…. OR you spend more $$$ to build band switchable compensation networks to improve the matching (Can be bulky and expensive but not always).? Pay me now of pay me later.? Many commercial SS Amps that cover 1-54 MHz complete still utilize some sort of compensation network in them to cover the large frequency range and it’s not apparent to the user… even with very good RF transistors (sometimes driven by the transformer material).?? All depends on the part.? Best to Simulate from the S params first.? It will tell you a lot. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ?
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From: [email protected] [mailto:[email protected]] On Behalf Of philip yates
Sent: Saturday, January 27, 2018 10:17 AM
To: [email protected]
Subject: Re: [BITX20] IRF510 amplifier failures ? So if they are " real RF transistors" probably worth the extra then ? ? On Sat, Jan 27, 2018 at 1:36 PM, K9HZ <bill@...> wrote: I don’t think it’s so much a matter of if they will work or not.? Both will work fine at 50 MHz (and above actually)… the issue is that the RD15HVF1 is a little flatter across the spectrum and from that perspective easier to design around and match.? I use them all the time and they are very easy parts to make work.? A pair will easily put out 30 watts 1-54 MHz if the rest of the design is correct. ? I’ve been thinking about and have had requests for a nice linear amplifier for the uBITx and these parts are cheap enough to use for that purpose too.? I originally designed one using two RD70HVF1 parts but the cheapest I’ve found them is $18 each.? Not a show stopper but the little brothers are cheaper.? If The parts were under $15 in large quantity, it would be a no brainer.? The auto tuner must be finished first though.? Oh, did I mention, the RD series devices are real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? From: [email protected] [mailto:[email protected]] On Behalf Of Lawrence Galea
Sent: Saturday, January 27, 2018 3:34 AM ? I was thinking about the RD15HVF1 so that it would be easier for people who want to try 50MHz and perhaps 70MHs where available with suitable mods to the μbitx. The RD16HHF1 appears to be? used in the Ukraine transverters as a PA in the 50MHz, 70MHz and 144 MHz transverters while the RD15HBF1 appears to be used in the 222MHz and 432MHz transverters.? I have the 50MHz and 70MHz transverters and they do work.
Two years ago I worked more than 40 stations on 70MHz (see my log on QRZ dot com) with a simple dipole at about 4M high on the roof fed with some 50 feet of RG58 coax. Last year I built a 5 element LFA Yagi for 70MHz but didn't have time to get on the air.? ? On Sat, Jan 27, 2018 at 3:41 AM, James Lawrie <lawriejk@...> wrote: Hello, That’s why I bought 10 ea... for the uBitxs I’ll probably get the others rated at over 30 MHz. Always nice to stock up on useful parts. Out of all listed on there website what would you recommend for HF/VHF use?
On Jan 26, 2018, at 19:56, K9HZ <bill@...> wrote:
The RD15HVF1 has a bit of a flatter input capacitance curve with frequency so its easier to keep constant gain over 1-54 MHz… but the RD16HHF1 is certainly a worthy part too.? Oh, did I mention, they are both real RF transistors? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? ? email:? bill@... ? ? On same site I found these, made for 30 MHz?RD16HHF1. Sooo I bought 10 of them, plan to try in Bix40 first. Data sheet even shows a reference amp design, and they are 12 volt like the other one. If it works I’ll let everyone know. ?
On Jan 26, 2018, at 11:32, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The RD15HVF1's should be operated at not much more than 12v.
At 12v, the IRF510's would survive just fine with no antenna connected.
That's an infinite VSWR.
So not obvious that this is a solution to blown FET's.
Though I do think the the Ids curves go up more slowly as Vgs increases on the RD15HF1's,
which makes RV2,RV3 not so touchy.
And the RD15HF1's might be easier to drive at 30mhz.
If you do swap them in, let us know how much power you get at 30mhz.
Jerry, KE7ER
On Fri, Jan 26, 2018 at 03:54 am, KD8CGH wrote: Wouldn't it be better to change to a RD15HVF1 for high VSWR
?
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Or build the wa2eby amp with two IRF510's in push pull.
Which works great and is pretty much flat through 30mhz
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On Sat, Jan 27, 2018 at 09:53 am, K9HZ wrote:
Well it’s this way.? You can either spend a little more on the transistor (with the nice input characteristics) and design with minimal parts (e.g. one set of broad band impedance matching transformers and bias network) to work over a large frequency range (1-54 MHz)…. Or you use a cheap motor switch like the 510 and live with the gain roll-off from mismatch (large del C / del Freq) with a fixed set of broad band I/O transformers…. OR you spend more $$$ to build band switchable compensation networks to improve the matching (Can be bulky and expensive but not always).? Pay me now of pay me later.? Many commercial SS Amps that cover 1-54 MHz complete still utilize some sort of compensation network in them to cover the large frequency range and it’s not apparent to the user… even with very good RF transistors (sometimes driven by the transformer material).?? All depends on the part.? Best to Simulate from the S params first.? It will tell you a lot.
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Bob Benedict, KD8CGH
James Lawrie
K9HZ