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The information you seek/suggest (4 points of connection and the recommended heat sink) are already in the build instructions… along with a schematic (to identify the 4 points of connection: RF IN, RF OUT, POWER +/-, and the PTT of 3V or more).? Because there are so many QRPers/groups that have opted to use this PA, I usually work with one of them… early on… ?and let them write detailed instructions for using this PA for their group if it warrants it.? ? I could spend the remainder of my life writing documentation on incorporating this PA into other people’s radios (even though most have figured it out without much discussion).? I have no intention of doing that since it is such a basic thing to do… and is not different than connecting an outboard linear amplifier to any radio. ?My time is better spent continuing to design more ham radio devices that are dirt cheap… giving more new amateurs a way to get on the air for the minimum $ with radios that are very well designed, and will last them a long time. ? What I do, however, is answer any and all questions from people while they are building and installing their PAs.? ? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
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From: [email protected] < [email protected]> On Behalf Of Gordon Gibby Sent: Sunday, October 8, 2023 12:44 PM To: [email protected]Cc: Jack Purdum <jjpurdum@...> Subject: Re: [AmateurRadioBuilders] [SoftwareControlledHamRadio] V010 vs V011 ? So what you’ll need to do is come up with mounting and connection information for people so that it becomes a real add-on kit. ? Just a board by it self is not sufficient. ? ?
On Oct 8, 2023, at 12:40, K9HZ <bill@...> wrote:
? Well Gordon, we meet again… ? Yes after suffering through the uBITx project with a bunch of people who really wanted to correct many of the design deficiencies (like the pre and PA section for example)… spending much of my time with simulations and redesigns.? I published many alternatives to that box that went much farther than Allisons…all dirt cheap to make. ?? I have a section out there with a few of my contributions. ? So after that project, I set out to build a small QRP PA section that was gain flat 1-54MHz, 20W PEP, operated from 12V for portable operation, capable of key-down forever, indestructible (open or short antenna jack), and DIRT CHEAP.? I did that last year.? The design is out in the files section of this forum… contains the schematic, BOM, build instructions, and GERBERS for everyone’s use.? FREE FREE FREE.? I even sell just the boards for $2, or a semi-kit that contains everything but the 1206 sized resistors and capacitors for under $20.? To date, I’ve sold over 800 of them at Hamvention and online… just received another 200 boards a day ago because I got another order for 50 from a place in the UK.? Picture attached. ? I saw Farhan at Hamvention (actually the QRP forum) and mentioned it to him… even sent him a kit GRATIS.? ?NADA… Dead silence.? I ORDERED TWO of his sBITx radios… cut the PA section out of one of them with a hack-saw and replaced it with mine.? Works perfectly, 20W PEP and you can’t blow it up no matter how hard you try.? Meanwhile I read the mail and see new people every day blowing up their sBITx.? There are some things that cannot be fixed.? This is not one of them.? Don’t get me wrong, Farhan is an outstanding RF designer.? He has really done a lot for radio kits. ? Its there.? Its available.? People know about it. ? I’m now working on a 100W module… same specs as the 20W module except 110W PEP… and guess what.? Its indestructible!? Almost ready for release.? Will be less than $100 by a lot and its actually smaller than the 20W module. ? ? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? ? It’s easy to see things to criticize. The trick here would be to create a upgrade kit that would make with the design and allow a better amplifier to be daughter boarded. ? That would give a great option for a lot of people and be a help! Gordon KX4Z?
On Oct 8, 2023, at 10:49, K9HZ <bill@...> wrote:
?This was not directed at the T41. Rather the likes of the Bitx family. ? ? 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: ? email:??bill@... ? ? The T41 design was a compromise on several fronts – primarily price vs performance., hence the situation with the power out. ? T41 is designed to be a teaching tool with flexibility and modularity. At the time we designed the PA, RF power transistors like the RD16HH were quite expensive and had limited availability. We did not feel that the price point with the extended frequency range at 20W suited our cost goals, hence the reduced power at 10M. T41 is meant to be QRP+, so some reduction of the higher end was the compromise to keep the price point down. We consciously made the decision to go with the less expensive output transistor design, knowing that the RF PA could easily be changed out if desired. ? By the way, the T41 costs several hundred dollars, not the many times higher price of ICOM or other commercial rigs. The popular ICOM 7300 goes for $1100 vs T41 at about $350.) ? That situation has changed somewhat, with the availability of $4 RD16HHs, making a redesign possible. Four years makes a difference. The K9HZ 20W amp is rated for 15W RMS and over 20W PEP, and it suits many builders. It is especially attractive for those who might wish to drive an external Linear. ? I personally also like the performance of the 20W K9HZ amp. It is alos pretty much indestructible. ?On the other hand Jack and I have made numerous contacts with the original T41 amp with excellent signal reports. ? We aim to provide choices. Regards, ? Al AC8GY ? From: K9HZ
Sent: Saturday, October 7, 2023 7:07 PM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] [SoftwareControlledHamRadio] V010 vs V011 ? Thanks Dave.? Yep, that little thing is a real gem.? I designed and built it because I just can’t stand hobby-ish radios that put out 40 watts on 7 MHz, and then 3 watts on 28 MHz.? It just means the designer didn’t care enough about his design to make it wide-banded… or didn’t know enough about RF design to make it happen.? Can you imagine what would happen if your brand new ICOM radio did that? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? ? Bill, this week I assembled two of the 20Wt amplifiers and they work great.? I was sweeping them at about 5watts with my NanoVNA and a 49dB attenuator (calibrated nano with the attenuator chain). I measure 48.6dB gain at 3.5MHz, 47.9dB at 7MHz, 47.8dB at 30MHz, and 43.7dB at 54MHz.? I am running with no filtering and see a lot of harmonic content at high frequency after adding C24 at 100pF (added to boost high freq performance), so I don't think I am seeing a 3dB roll off at 50MHz.? Thank you for you work on this.? I look forward to the v12 boards. I will start next week on programming the Teensy4.1 and connecting it to the display. ? On Sat, Oct 7, 2023 at 12:32?PM K9HZ <bill@...> wrote: I also have a conference this week in Denver so things will pause for a few days on my end. ? I did send schematics to Al to review yesterday though so trying to multitask and get stuff out ASAP. ? I did receive an order of 20W PA boards yesterday ?so those are back in stock. ? ? 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: ? email:??bill@... ? ? > Once the boards are finalized and I can get the Gerbers > I will start getting boards made for UK and Europe. And, for our Canadian hams...? Once the new boards are finalized and available from K9HZ, I'm happy to offer to import and distribute them in a new round. I'll also be away for a work conference for the next week ( I plan to sneak out to get a couple POTA activations in though, so look for VA3NCA/W9 on spots) so probably won't be very quick to reply, but I will start collecting item orders and quantities once Bill's ready, and I'm back and caught up after travel ? -------- Original message -------- Date: 2023-10-07 10:01 a.m. (GMT-05:00) Subject: Re: [SoftwareControlledHamRadio] V010 vs V011 Once the boards are finalized and I can get the Gerbers I will start getting boards made for UK and Europe. I am in Dubrovnik for the next few days but once I have them I can get started straight away. ? On Sat, 7 Oct 2023, 15:31 K9HZ, <bill@...> wrote: I started sending final production schematics to Al as of last night.? It wont be long.? A few things left to resolve on the RF board and we can go into production. ? ? 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: ? email:??bill@... ? ?I can give you some ideas.
I know several people worked on the project is small steps as I did.
First, buy the Teensy 4.1 and the display.? Using a breadboard and a power supply, you can connect the Display to the Teensy and load the software.
Setting up the IDE and the libraries and getting the Teensy properly programmed and the display working is a major step.? Getting the Display delivered may take weeks.
Next I would build and test the power supply board, and then the Main board.? Now see if the Teensy in the Main board successfully drives the display.
Build the Switch Matrix board, which is easy, and connect to the Main board and see if you can get past the switch matrix calibration.
Also another huge step is getting the 3D printed case built and assembled.
Regarding the BOMs, what we did in the early days was collaborate quite a lot in the discussions here to get the correct parts.? There are errors in the published BOMs, and also
parts which are no longer available and need substitutes.
4SQRP should be publishing their BOMs soon, and they should be quite accurate, being adjusted for the current supply chain issues.
Another idea would be to proceed through the breadboading of the display and IDE setup and programming, at which time the V012 boards could become available.
I don't know the current schedule for that to happen, but I do know it will take you a while just to get to the working breadboard stage.
--
73 Greg KF5N
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Hi Dr Schmidt, and everyone here!
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I'm finally getting to start the build of your 20W PA semi-kit. I will eventually use it with my T41 build as I get there, but would like to experiment a little with it as a standalone amp in the meantime.
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Does anyone have a generic block diagram on how this would integrate into an arbitrary other radio? I assume the following needs consideration:? rf-in power matching ( via the input power pad on board)? , rf-out lpf , ptt voltage interface conversion (if necessary), and TR switching? Anything else that would need to be handled?
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If a specific other qrp radio integration has been documented someplace, I'd be interested in reviewing that too!
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Thanks! and 73, Wayde VA3NCA/AD2GX?
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Hi Wade… the Assembly manual covers all of these topics…?? IF you need help with the input attenuator, just ask for the specific example (formulas are in the manual)… ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
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From: [email protected] <[email protected]> On Behalf Of Wayde VA3NCA/AD2GX via groups.io
Sent: Tuesday, February 11, 2025 11:47 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] K9HZ PA? Hi Dr Schmidt, and everyone here! I'm finally getting to start the build of your 20W PA semi-kit. I will eventually use it with my T41 build as I get there, but would like to experiment a little with it as a standalone amp in the meantime. Does anyone have a generic block diagram on how this would integrate into an arbitrary other radio? I assume the following needs consideration:? rf-in power matching ( via the input power pad on board)? , rf-out lpf , ptt voltage interface conversion (if necessary), and TR switching? Anything else that would need to be handled? If a specific other qrp radio integration has been documented someplace, I'd be interested in reviewing that too! Thanks! and 73, Wayde VA3NCA/AD2GX?
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Thank-you Bill,
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I'm working through the build, and would like to ask; Does anyone have some guidance on a good target input drive power to configure the input pad for? I have 2 K9HZ kits and I plan to build the first one, initially for use with a qrp rig, which can be set in 100mW increments from 0.1W to 5W. ( Although, I'm not convinced of the accuracy of those 100mW increments, necessarily).
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Is there a "typical" , practical input drive current that is used, a rule of thumb or something like that?
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Thanks,Wayde VA3NCA/AD2GX
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Wayde,
The attenuator on the amp is made with 1/8 W SMD resistors, so 100mW would about the most power you could drive it with. It only needs 1 mW to drive it to full power so you would have to dissipate nearly all the 100mW of drive in the attenuator. I think you need to consider an external attenuator which absorbs most of the drive power. In any case, if you already have a 5W rig, why do you need a 20 W amp? For 6dB?
Gary
W9TD
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That should not be a big deal unless the mode is a digital continuous one like FT8 etc. ?
You need 8 watts to drive my 100W PA to full power so the 20W intermediate stage is the right module for that purpose. ?
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: www.VillaGrandPiton.com
email:??bill@... ?
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On Feb 22, 2025, at 3:30?PM, Gary via groups.io <w9td@...> wrote:
? Wayde,
The attenuator on the amp is made with 1/8 W SMD resistors, so 100mW would about the most power you could drive it with. It only needs 1 mW to drive it to full power so you would have to dissipate nearly all the 100mW of drive in the attenuator. I think you need to consider an external attenuator which absorbs most of the drive power. In any case, if you already have a 5W rig, why do you need a 20 W amp? For 6dB?
Gary
W9TD
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Well, this is the kit I have, and it's a nice one (thanks Bill!) Having a use in mind for it gives a practical goal to the building exercise ( until my T41 is further along that is! ), and 6dB is 6dB after-all when you're out in a park? :-D?
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I'll look into an external attenuator, perhaps 30dB / 20W or so out front, might let me set 1W or a little less out, and give some room below for inaccurate power settings.
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73! Wayde VA3NCA/AD2GX
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Thanks for the suggestion, I'll try to find a good flange attenuator to bolt to the heatsink. My heatsink is an e-waste salvage, and a bit bigger than needed anyhow, so it has enough space to fit it nicely.
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73! Wayde VA3NCA/AD2GX
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These are not cheap devices. ?
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: www.VillaGrandPiton.com
email:??bill@... ?
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On Feb 22, 2025, at 10:16?PM, Wayde VA3NCA/AD2GX via groups.io <wayde@...> wrote:
? Thanks for the suggestion, I'll try to find a good flange attenuator to bolt to the heatsink. My heatsink is an e-waste salvage, and a bit bigger than needed anyhow, so it has enough space to fit it nicely.
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73! Wayde VA3NCA/AD2GX
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I guess I did say "good" device in my reply ( lol ! ) and good devices would definitely be expensive... I was thinking of trying ( and testing... ) something like one of these (for example):?
?
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Assuming it lives up to its claims... Is this the type of thing you were thinking about @Jerry , when you mentioned trying a flange attenuator?
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Thanks for all the guidance, everyone , and for the 20W Amp kit in the first place Bill!?
73! Wayde VA3NCA/AD2GX
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On 2025-02-23 07:01, K9HZ wrote: These are not cheap devices. $3 to $15 on Aliexpress. And they're the right tool for the job. - Jerry, KF6VB
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: www.VillaGrandPiton.com
email: bill@...
On Feb 22, 2025, at 10:16?PM, Wayde VA3NCA/AD2GX via groups.io
<wayde@...> wrote: ?
Thanks for the suggestion, I'll try to find a good flange attenuator
to bolt to the heatsink. My heatsink is an e-waste salvage, and a
bit bigger than needed anyhow, so it has enough space to fit it
nicely.
73! Wayde VA3NCA/AD2GX
Links:
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[1] /g/AmateurRadioBuilders/message/6105
[2] /mt/101838544/243852
[3] /g/AmateurRadioBuilders/post
[4] /g/AmateurRadioBuilders/editsub/243852
[5]
/g/AmateurRadioBuilders/leave/11522011/243852/920863695/xyzzy
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Most welcome Wayde! ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
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From: [email protected] <[email protected]> On Behalf Of Wayde VA3NCA/AD2GX via groups.io
Sent: Sunday, February 23, 2025 10:46 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] K9HZ PA? I guess I did say "good" device in my reply ( lol ! ) and good devices would definitely be expensive... I was thinking of trying ( and testing... ) something like one of these (for example):? Assuming it lives up to its claims... Is this the type of thing you were thinking about @Jerry , when you mentioned trying a flange attenuator? Thanks for all the guidance, everyone , and for the 20W Amp kit in the first place Bill!?
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I think 30dB is probably excessive.
Here's a 10dB Florida RF one on Ebay
- Jerry, KF6VB
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Bill,
What about bypassing the driver? Can you share what the input power requirement would be after it, and/or how to do so? Can one basically bypass it and connect C1 to the input of T2, or is there impedance transformation needed??
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I'm struggling to get power low enough on my supply side without insane attenuation, and I'd rather not waste as much power/heat. Thinking of a Class C configuration...and seems every RD16 and similar amp in this power range these days has a driver amp on board for much lower inputs.
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Thanks for your time.?
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-Nate
N8BTR
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Below in RED ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
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From: [email protected] <[email protected]> On Behalf Of Nate Reik via groups.io
Sent: Tuesday, March 18, 2025 12:52 PM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] K9HZ PA? What about bypassing the driver? Can you share what the input power requirement would be after it You need about 400 mW to drive the RD16’s to full power, and/or how to do so? Can one basically bypass it and connect C1 to the input of T2 Yes, T2 basically a 50ohm to 50 ohm transformer, or is there impedance transformation needed NOPE?? I'm struggling to get power low enough on my supply side without insane attenuation, and I'd rather not waste as much power/heat. Thinking of a Class C configuration Only for CW!...and seems every RD16 and similar amp in this power range these days has a driver amp on board for much lower inputs Because they are much more universal.? Very few transmitters put out 400 Mw… they are much more in the 1 mW range.
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K9HZ
Wayde VA3NCA/AD2GX
Gary