Dummy load antenna


KF5CSW
 

Pardon me for my lack of intelligence beyond that of General Class license... I'd never be able to obtain Extra...
 
I would *love* to participate in the hotel room qrp activity at the convention this year (my first). I only see a hand drawn schematic of the  Ozark Con DL special. There's some blue text on that webpage (http://www.wa0itp.com/dlspecial.html). If it's supposed to be a link, it doesn't seem to be active.
 
I'm unfamiliar with the 50 ohm resistor used.  My first thought would have been a single 50 ohm resistor. But you have to dissipate a little heat, right? Then I started looking how dummy loads that are *not* intended to radiate at all are constructed. I found various diy dummy load resistors that involve anywhere from 4 to maybe 20 resistors run in parallel that would give 50 ohms. I could probably build that myself. I do see some kits available for this purpose, but they also contain some additional elements like a diode-capacitor rectifier for peak voltage measurements... where to connect the wire antenna part in those setups? I do see on some of the schematics that there are pins for RF and for ground.  Maybe connect to those? However, Those ones have a BNC male connector, which wouldn't work for that setup (see below).
 
Qrpme's Dummy Load Construction Set looks intriguing and might be a solution in itself. However, the provided connector in the kit is an RCA jack. At the time of the convention, the only thing I will have that works on 40m is my Icom 718 set to low power, and that uses a SO-239; I'm stuck with a piece of coax that has PL-259's at each end. I don't know if an adapter (RCA plug or BNC female) throws off my impedance.
 
If I made any technical mistakes in this post, please forgive me.
 
Thank you :)
John Vogel
KF5CSW
Roger's, AR


Karl Schwab
 

How about using Crickets at the convention?  Karl/KO8S

On Fri, Mar 11, 2022 at 3:54 PM KF5CSW <rehabnurse63@...> wrote:
Pardon me for my lack of intelligence beyond that of General Class license... I'd never be able to obtain Extra...
 
I would *love* to participate in the hotel room qrp activity at the convention this year (my first). I only see a hand drawn schematic of the  Ozark Con DL special. There's some blue text on that webpage (http://www.wa0itp.com/dlspecial.html). If it's supposed to be a link, it doesn't seem to be active.
 
I'm unfamiliar with the 50 ohm resistor used.  My first thought would have been a single 50 ohm resistor. But you have to dissipate a little heat, right? Then I started looking how dummy loads that are *not* intended to radiate at all are constructed. I found various diy dummy load resistors that involve anywhere from 4 to maybe 20 resistors run in parallel that would give 50 ohms. I could probably build that myself. I do see some kits available for this purpose, but they also contain some additional elements like a diode-capacitor rectifier for peak voltage measurements... where to connect the wire antenna part in those setups? I do see on some of the schematics that there are pins for RF and for ground.  Maybe connect to those? However, Those ones have a BNC male connector, which wouldn't work for that setup (see below).
 
Qrpme's Dummy Load Construction Set looks intriguing and might be a solution in itself. However, the provided connector in the kit is an RCA jack. At the time of the convention, the only thing I will have that works on 40m is my Icom 718 set to low power, and that uses a SO-239; I'm stuck with a piece of coax that has PL-259's at each end. I don't know if an adapter (RCA plug or BNC female) throws off my impedance.
 
If I made any technical mistakes in this post, please forgive me.
 
Thank you :)
John Vogel
KF5CSW
Roger's, AR
 


Johnny AC0BQ
 

Ge John
The link you sent works for me.
Terry’s radiating dummy load is a piece of wire about 10 feet long, with a 50 ohm resistor in series with the wire connected to your BNC at your radio.

Turn your power down to a watt or so and transmit room to room and put a QSL card in the table or their door.

Also you can contact K0N the club station down in the knights room.

72
Johnny 

On Fri, Mar 11, 2022 at 2:54 PM KF5CSW <rehabnurse63@...> wrote:
Pardon me for my lack of intelligence beyond that of General Class license... I'd never be able to obtain Extra...
 
I would *love* to participate in the hotel room qrp activity at the convention this year (my first). I only see a hand drawn schematic of the  Ozark Con DL special. There's some blue text on that webpage (http://www.wa0itp.com/dlspecial.html). If it's supposed to be a link, it doesn't seem to be active.
 
I'm unfamiliar with the 50 ohm resistor used.  My first thought would have been a single 50 ohm resistor. But you have to dissipate a little heat, right? Then I started looking how dummy loads that are *not* intended to radiate at all are constructed. I found various diy dummy load resistors that involve anywhere from 4 to maybe 20 resistors run in parallel that would give 50 ohms. I could probably build that myself. I do see some kits available for this purpose, but they also contain some additional elements like a diode-capacitor rectifier for peak voltage measurements... where to connect the wire antenna part in those setups? I do see on some of the schematics that there are pins for RF and for ground.  Maybe connect to those? However, Those ones have a BNC male connector, which wouldn't work for that setup (see below).
 
Qrpme's Dummy Load Construction Set looks intriguing and might be a solution in itself. However, the provided connector in the kit is an RCA jack. At the time of the convention, the only thing I will have that works on 40m is my Icom 718 set to low power, and that uses a SO-239; I'm stuck with a piece of coax that has PL-259's at each end. I don't know if an adapter (RCA plug or BNC female) throws off my impedance.
 
If I made any technical mistakes in this post, please forgive me.
 
Thank you :)
John Vogel
KF5CSW
Roger's, AR
 

--
Check out the 4SQRP website at 4sqrp.com


Curt
 

John

You essentially got it. 

You need a 50 ohm resistor across the rig’s antenna connector, that can dissipate its power. For less than a half watt, one watt resistor works. Otherwise you have the idea to parallel them. 

The diode, where included, is to allow measuring appropriate output power, not needed here. 

Now add some wire at the end to allow the tiny leakage to radiate. Yes even just a dummy load radiates a little. But some wire helps further. Meanwhile most of the RF is heat. 

Curt


W6BOW
 

Should the 50 ohm resistor be non-inductive?


-----Original Message-----
From: Curt via groups.io <wb8yyy@...>
To: main@4SQRP.groups.io
Sent: Sun, Mar 13, 2022 12:22 pm
Subject: Re: [4SQRP] Dummy load antenna

John

You essentially got it. 

You need a 50 ohm resistor across the rig’s antenna connector, that can dissipate its power. For less than a half watt, one watt resistor works. Otherwise you have the idea to parallel them. 

The diode, where included, is to allow measuring appropriate output power, not needed here. 

Now add some wire at the end to allow the tiny leakage to radiate. Yes even just a dummy load radiates a little. But some wire helps further. Meanwhile most of the RF is heat. 

Curt


Johnny AC0BQ
 

It would be best.
72
Johnny ACØBQ 

On Sun, Mar 13, 2022 at 7:28 PM W6BOW via groups.io <DBuckter=aol.com@groups.io> wrote:
Should the 50 ohm resistor be non-inductive?


-----Original Message-----
From: Curt via groups.io <wb8yyy=yahoo.com@groups.io>
To: main@4SQRP.groups.io
Sent: Sun, Mar 13, 2022 12:22 pm
Subject: Re: [4SQRP] Dummy load antenna

John

You essentially got it. 

You need a 50 ohm resistor across the rig’s antenna connector, that can dissipate its power. For less than a half watt, one watt resistor works. Otherwise you have the idea to parallel them. 

The diode, where included, is to allow measuring appropriate output power, not needed here. 

Now add some wire at the end to allow the tiny leakage to radiate. Yes even just a dummy load radiates a little. But some wire helps further. Meanwhile most of the RF is heat. 

Curt

--
Check out the 4SQRP website at 4sqrp.com


KF5CSW
 

Thank you everyone for all the answers.  Looking forward to Ozarkcon :)

73
John
KF5CSW 
Rogers, AR

On Sun, Mar 13, 2022, 7:39 PM Johnny AC0BQ <jomatlock@...> wrote:
It would be best.
72
Johnny ACØBQ 

On Sun, Mar 13, 2022 at 7:28 PM W6BOW via groups.io <DBuckter=aol.com@groups.io> wrote:
Should the 50 ohm resistor be non-inductive?


-----Original Message-----
From: Curt via groups.io <wb8yyy=yahoo.com@groups.io>
To: main@4SQRP.groups.io
Sent: Sun, Mar 13, 2022 12:22 pm
Subject: Re: [4SQRP] Dummy load antenna

John

You essentially got it. 

You need a 50 ohm resistor across the rig’s antenna connector, that can dissipate its power. For less than a half watt, one watt resistor works. Otherwise you have the idea to parallel them. 

The diode, where included, is to allow measuring appropriate output power, not needed here. 

Now add some wire at the end to allow the tiny leakage to radiate. Yes even just a dummy load radiates a little. But some wire helps further. Meanwhile most of the RF is heat. 

Curt

--
Check out the 4SQRP website at 4sqrp.com