Re: Dummy Load Resistors - 1 pound sack
On Sun, Nov 1, 2020 at 03:43 PM, Bill Cromwell wrote:
Hi,
... . Don't skimp with your dummy load or your power supply.
73,
Hi Bill
it's true ! never skimp on such useful and simple tools!
But ... if you want to build this accessory too, use suitable resistors built for RF, today you can find new ones for a few dollars !!!
I understand the charm of paralleling dozens of resistors and looking for the most amazing ways to match the load to the correct impedance, without capacitance or parasitic inductances like we did 40 or 50 years ago, but today it doesn't make sense anymore, using the right component costs a lot less effort and probably even less dollars to get a ready-made RF load, just add a suitable heat sink and 100W or 250W can be achieved with just one resistor!
Good job everyone !!!
73 IW4AJR Loris
|
hello
Here, dunny load in a?converse box with linseed oil
cdt
|
Better choice quartz for 11.059 filter
Hello, I will change my quartz filter on my home Ubitx. I will go from 12MHZ to 11.59 MHZ.I tested about 20 quartz.To compare and cross to my results, what are the 8 best for you? 8 numbers!The test is done in parallel and serial oscillation.
cdt
?
-1
A peine compr¨¦hensible
Compr¨¦hensible, mais avec des erreurs
Presque correct
Correct
?
|
Re: Dummy Load Resistors - 1 pound sack
Hi,
Even though I have only 100 watt output class transmitters as my biggest guns here I have almost never run more than 75 watts. Several of my transmitters will not put out even close to 100 watts with a few in the two to ten watt range. I always use one of those big, commercially made for RF, 100 watt resistors. It is a sad fact of of life that we cannot put 10 pounds of balogna in a 1 pound sack. My shielded dummy load from R. L. Drake has been in business for decades and mostly never gets warm. The MFJ resistor I have looks identical to the one in the Drake. Same size, same color, same specs. Don't skimp with your dummy load or your power supply.
73,
Bill KU8H
bark less - wag more
toggle quoted message
Show quoted text
On 11/1/20 8:47 AM, Jack, W8TEE via groups.io wrote: Careful! Al and I experimented with 500W units, putting only 100W into it. Within a few seconds, the top half of the resistor went into low-earth orbit. Even at 1/10 the rated output, you need a pretty good heatsink. In the new /Projects/ book, we have a QRP mini DL and watt meter that we rate at about 25W for 10 seconds and uses a 250W RF resistor. It still has a fairly large heat sink:
Inline image
Jack, W8TEE
On Sunday, November 1, 2020, 1:11:22 AM EST, Raj vu2zap <rajendrakumargg@...> wrote:
My pick,
Easily available on the 'bay for a few bucks! from a few watts to kilowatts are available.
All you need is a heatsink.
Emacs!
At 01/11/2020, you wrote:
Good info. But when you build one of those in the image, I suggest that you leave the leads long since they help dissipate the heat.
Bob ¡ª KK5R
On Saturday, October 31, 2020, 11:08:39 AM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:
We did a similar DL for the November 2018 QST article which also had a watt meter built in. By putting the resistor pack in mineral oil, we were able to run 200W into it for 5 minutes without failure.
Inline image
Jack, W8TEE
On Saturday, October 31, 2020, 10:43:28 AM EDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
Mouser used to sell Xicon 3W metal oxide resistors in small quantities,
now they have a minimum buy of 100 at $0.10 each.? Darn!
? 283-100-RC $0.10/100
But they do have a KOA-Speer in single units, haven't gotten any but they look good:
660-MOS3CT631R101J KOA Speer?? 3W radial metal oxide,? $0.20/1 $0.15/100
Tayda has a no-name product at $0.06 each with single unit pricing,
? SKU A-2549????? $0.06/1
Those are all 100 ohm, two in parallel from Tayda at $0.12 should be suitable for use with a uBitx.
20 of the 1000 ohm variant in parallel are 1000/20=50 ohm, good for 20*3=60 Watts continuous.
Also some offerings in metal oxide resistors at 2 Watts instead of 3 Watts.
If you want to spend more than $0.12, here's some proper RF dummy loads for 100W or more at under $10:
Will need a good heat sink and thermal paste for those guys.
Search for "RFP Dummy Load" to find other options.
To spend less than $0.12 and have it working today, check out WB9SBD's baking soda bath:
/g/BITX20/message/83207
Jerry, KE7ER
--
Jack, W8TEE --
Jack, W8TEE
|
Careful! Al and I experimented with 500W units, putting only 100W into it. Within a few seconds, the top half of the resistor went into low-earth orbit. Even at 1/10 the rated output, you need a pretty good heatsink. In the new Projects book, we have a QRP mini DL and watt meter that we rate at about 25W for 10 seconds and uses a 250W RF resistor. It still has a fairly large heat sink:
Jack, W8TEE
On Sunday, November 1, 2020, 1:11:22 AM EST, Raj vu2zap <rajendrakumargg@...> wrote:
My pick,
Easily available on the 'bay for a few bucks! from a few watts to
kilowatts are available.
All you need is a heatsink.
At 01/11/2020, you wrote:
Good info. But when you build
one of those in the image, I suggest that you leave the leads long since
they help dissipate the heat.
Bob ¡ª KK5R
On Saturday, October 31, 2020, 11:08:39 AM EDT, Jack, W8TEE via groups.io
<jjpurdum@...> wrote:
We did a similar DL for the November 2018 QST article which also had a
watt meter built in. By putting the resistor pack in mineral oil, we were
able to run 200W into it for 5 minutes without failure.
![Inline image]()
Jack, W8TEE
On Saturday, October 31, 2020, 10:43:28 AM EDT, Jerry Gaffke via
groups.io <jgaffke@...> wrote:
Mouser used to sell Xicon 3W metal oxide resistors in small
quantities,
now they have a minimum buy of 100 at $0.10 each.? Darn!?
? 283-100-RC????????
$0.10/100
But they do have a KOA-Speer in single units, haven't gotten any but they
look good:
?
660-MOS3CT631R101J?????????????????????????????????
KOA Speer?? 3W radial metal oxide,? $0.20/1?
$0.15/100
Tayda has a no-name product at $0.06 each with single unit pricing,
? SKU A-2549????? $0.06/1
Those are all 100 ohm, two in parallel from Tayda at $0.12 should be
suitable for use with a uBitx.
20 of the 1000 ohm variant in parallel are 1000/20=50 ohm, good for
20*3=60 Watts continuous.
Also some offerings in metal oxide resistors at 2 Watts instead of 3
Watts.
If you want to spend more than $0.12, here's some proper RF dummy loads
for 100W or more at under $10:
???
???
Will need a good heat sink and thermal paste for those guys.
Search for "RFP Dummy Load" to find other options.
To spend less than $0.12 and have it working today, check out WB9SBD's
baking soda bath:
?
/g/BITX20/message/83207
Jerry, KE7ER
?
--
Jack, W8TEE
--
Jack, W8TEE
|
On Sat, Oct 31, 2020 at 11:33 PM, Christopher Miller wrote:
This is a little off the topic but I have a 100 watt dry load from MFJ. Can I submerge it in mineral oil to help it handle it¡¯s rated input for longer?
Yes, you can.? MFJ sells a "cantenna" type of dummy load and teardown on it stated that the resistor looked the same as the one in the dry dummy load. https://mfjenterprises.com/products/mfj-250
|
You need a pretty serious heat sink to dissipate 500W though!
I'm planning to try doing a 100W one with a leftover CPU cooler to?get rid of the heat. That should give me a relatively compact dummy load for that power level, though it will require power for the fan.
My pick,
Easily available on the 'bay for a few bucks! from a few watts to
kilowatts are available.
All you need is a heatsink.
At 01/11/2020, you wrote:
Good info. But when you build
one of those in the image, I suggest that you leave the leads long since
they help dissipate the heat.
Bob ¡ª KK5R
On Saturday, October 31, 2020, 11:08:39 AM EDT, Jack, W8TEE via
<jjpurdum=[email protected]> wrote:
We did a similar DL for the November 2018 QST article which also had a
watt meter built in. By putting the resistor pack in mineral oil, we were
able to run 200W into it for 5 minutes without failure.
![Inline image]()
Jack, W8TEE
On Saturday, October 31, 2020, 10:43:28 AM EDT, Jerry Gaffke via
<jgaffke=[email protected]> wrote:
Mouser used to sell Xicon 3W metal oxide resistors in small
quantities,
now they have a minimum buy of 100 at $0.10 each.? Darn!?
? 283-100-RC????????
$0.10/100
But they do have a KOA-Speer in single units, haven't gotten any but they
look good:
?
660-MOS3CT631R101J?????????????????????????????????
KOA Speer?? 3W radial metal oxide,? $0.20/1?
$0.15/100
Tayda has a no-name product at $0.06 each with single unit pricing,
? SKU A-2549????? $0.06/1
Those are all 100 ohm, two in parallel from Tayda at $0.12 should be
suitable for use with a uBitx.
20 of the 1000 ohm variant in parallel are 1000/20=50 ohm, good for
20*3=60 Watts continuous.
Also some offerings in metal oxide resistors at 2 Watts instead of 3
Watts.
If you want to spend more than $0.12, here's some proper RF dummy loads
for 100W or more at under $10:
???
???
Will need a good heat sink and thermal paste for those guys.
Search for "RFP Dummy Load" to find other options.
To spend less than $0.12 and have it working today, check out WB9SBD's
baking soda bath:
?
/g/BITX20/message/83207
Jerry, KE7ER
?
--
Jack, W8TEE
|
My pick,
Easily available on the 'bay for a few bucks! from a few watts to
kilowatts are available.
All you need is a heatsink.
At 01/11/2020, you wrote:
Good info. But when you build
one of those in the image, I suggest that you leave the leads long since
they help dissipate the heat.
Bob ¡ª KK5R
On Saturday, October 31, 2020, 11:08:39 AM EDT, Jack, W8TEE via groups.io
<jjpurdum@...> wrote:
We did a similar DL for the November 2018 QST article which also had a
watt meter built in. By putting the resistor pack in mineral oil, we were
able to run 200W into it for 5 minutes without failure.
Jack, W8TEE
On Saturday, October 31, 2020, 10:43:28 AM EDT, Jerry Gaffke via
groups.io <jgaffke@...> wrote:
Mouser used to sell Xicon 3W metal oxide resistors in small
quantities,
now they have a minimum buy of 100 at $0.10 each.? Darn!?
? 283-100-RC????????
$0.10/100
But they do have a KOA-Speer in single units, haven't gotten any but they
look good:
?
660-MOS3CT631R101J?????????????????????????????????
KOA Speer?? 3W radial metal oxide,? $0.20/1?
$0.15/100
Tayda has a no-name product at $0.06 each with single unit pricing,
? SKU A-2549????? $0.06/1
Those are all 100 ohm, two in parallel from Tayda at $0.12 should be
suitable for use with a uBitx.
20 of the 1000 ohm variant in parallel are 1000/20=50 ohm, good for
20*3=60 Watts continuous.
Also some offerings in metal oxide resistors at 2 Watts instead of 3
Watts.
If you want to spend more than $0.12, here's some proper RF dummy loads
for 100W or more at under $10:
???
???
Will need a good heat sink and thermal paste for those guys.
Search for "RFP Dummy Load" to find other options.
To spend less than $0.12 and have it working today, check out WB9SBD's
baking soda bath:
?
/g/BITX20/message/83207
Jerry, KE7ER
?
--
Jack, W8TEE
|
For anyone interested, here is the parts kit for the timer:
On Saturday, October 31, 2020, 10:32:27 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
This is from Jameco. Should be interesting...
|
I wondered the same thing IF I got the MFJ dry dummy load. I don't see any reason why you can't but it might get messy. If I did it, I'm place the dummy load into the container of oil vertically and probably leave the top of the container open. Otherwise, maybe you can unmount the components in the dummy load and use the can lid to remount the components. Might need to find a deeper can if the components are too long. At least the container would be closed and keep the oil from spilling out. Just make sure the container has a "weep hole" in the top to allow the container to breathe and avoid pressure from building up in the can in case the can/oil gets hot.
Bob ¡ª KK5R
On Sunday, November 1, 2020, 12:33:53 AM EDT, Christopher Miller <djmalak2k6@...> wrote:
This is a little off the topic but I have a 100 watt dry load from MFJ. Can I submerge it in mineral oil to help it handle it¡¯s rated input for longer? Or should I build a new load? I could also just buy a cantenna at some point.
Chris?
|
This is a little off the topic but I have a 100 watt dry load from MFJ. Can I submerge it in mineral oil to help it handle it¡¯s rated input for longer? Or should I build a new load? I could also just buy a cantenna at some point.
Chris?
|
It¡¯s almost identical to the Hycas AGC circuit that was published in QST several years ago. ? MRM ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of AndyH Sent: Saturday, October 31, 2020 6:47 PM To: [email protected]Subject: Re: [BITX20] AGC circuit to try? ? Unfortunately, the files actually aren't on the listed group.? They are, however, in the files section of the JackAl group.? One has to be a member of the group to access the files, but membership isn't moderated and access is instant.
/g/JackAl/files/JackAl%20Documentation%20and%20Code%20Files
It's an interesting AGC design - it takes audio from the top of the volume control pot and varies RF prior to the crystal filter.? Has anyone successfully implemented this board and AGC scheme on a ?BITX?? I can't find any reports of success or of how the AGC performs on the group dedicated to the board, and can't find any indication that it's ever been installed on a V5 or V6 radio.
73, Andy
On Fri, Oct 30, 2020 at 10:19 PM, Jack, W8TEE wrote: Al and I posted the JackAl schematics and code on my site: SoftwareControlledHamRadio: | ? | SoftwareControlledHamRadio groups.io GroupThis group is for anyone who is interested in using software in ham radio projects. |
|
|
On Friday, October 30, 2020, 6:30:11 PM EDT, Curt via groups.io <wb8yyy@...> wrote: George
if you are enthusiastic about an IF AGC in the ubitx-- use a search engine (or look here in files) to find the Jackal schematic - it has an IF AGC circuit that could be employed, that seems to be derived from the hybrid cascode (W7ZOI) with less stages as I recall.?
I find with an audio filter and audio AGC the ubitx is a decent rig to do some casual HF.? But do explore circuits to your fancy.? Speaking of the hycas, I built one a few years ago - got distracted by our club build of v4 ubitx (that needed some effort to tame) - so I need to think through what band(s) I will deploy the hycas in a receiver.?
73 curt
--
Jack, W8TEE
-- ¡_. _._
|
Found it here:
But, what value did you use and what value?
K4EAA offered a set of resistors that I used in a Lowes empty quart can and mineral oil that had a banana jack and a bridge that you could use with a multimeter and calculate the power out into the dummy load. My main dummy load. If he responds to my message, I will post here.
Bob ¡ª KK5R
On Saturday, October 31, 2020, 1:51:13 PM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:
David:
If you just use 32966376132 in the Ali search bar, it finds the item.
Jack, W8TEE
On Saturday, October 31, 2020, 1:37:56 PM EDT, N8DAH <dherron@...> wrote:
I have been using these for my dummy loads and they have been pretty darn surprising.
https://www.aliexpress.com/item/32966376132.html?spm=a2g0o.productlist.0.0.1a9e5261YmP5gm&algo_pvid=d2007a98-6b86-4a1d-80ce-61348dbc4deb&algo_expid=d2007a98-6b86-4a1d-80ce-61348dbc4deb-9&btsid=0bb0622d16041657591331983eada4&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
--
David
?N8DAH
--
Jack, W8TEE
|
Good info. But when you build one of those in the image, I suggest that you leave the leads long since they help dissipate the heat.
Bob ¡ª KK5R
On Saturday, October 31, 2020, 11:08:39 AM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:
We did a similar DL for the November 2018 QST article which also had a watt meter built in. By putting the resistor pack in mineral oil, we were able to run 200W into it for 5 minutes without failure.
On Saturday, October 31, 2020, 10:43:28 AM EDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
Mouser used to sell Xicon 3W metal oxide resistors in small quantities, now they have a minimum buy of 100 at $0.10 each.? Darn!?? ? 283-100-RC?? ? ? ? $0.10/100 But they do have a KOA-Speer in single units, haven't gotten any but they look good: ? 660-MOS3CT631R101J? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? KOA Speer? ?3W radial metal oxide,? $0.20/1? $0.15/100 Tayda has a no-name product at $0.06 each with single unit pricing, ? SKU A-2549? ? ? $0.06/1 Those are all 100 ohm, two in parallel from Tayda at $0.12 should be suitable for use with a uBitx. 20 of the 1000 ohm variant in parallel are 1000/20=50 ohm, good for 20*3=60 Watts continuous. Also some offerings in metal oxide resistors at 2 Watts instead of 3 Watts. If you want to spend more than $0.12, here's some proper RF dummy loads for 100W or more at under $10: ? ?? ? ? Will need a good heat sink and thermal paste for those guys. Search for "RFP Dummy Load" to find other options. To spend less than $0.12 and have it working today, check out WB9SBD's baking soda bath: ?? /g/BITX20/message/83207Jerry, KE7ER ?
--
Jack, W8TEE
|
This is from Jameco. Should be interesting...
|
Unfortunately, the files actually aren't on the listed group.? They are, however, in the files section of the JackAl group.? One has to be a member of the group to access the files, but membership isn't moderated and access is instant. /g/JackAl/files/JackAl%20Documentation%20and%20Code%20FilesIt's an interesting AGC design - it takes audio from the top of the volume control pot and varies RF prior to the crystal filter.? Has anyone successfully implemented this board and AGC scheme on a ?BITX?? I can't find any reports of success or of how the AGC performs on the group dedicated to the board, and can't find any indication that it's ever been installed on a V5 or V6 radio. 73, Andy
On Fri, Oct 30, 2020 at 10:19 PM, Jack, W8TEE wrote:
George:
?
Al and I posted the JackAl schematics and code on my site: SoftwareControlledHamRadio:
?
?
|
|
| ? |
SoftwareControlledHamRadio groups.io Group
This group is for anyone who is interested in using software in ham radio projects.
|
|
|
On Friday, October 30, 2020, 6:30:11 PM EDT, Curt via groups.io <wb8yyy@...> wrote:
?
?
George
if you are enthusiastic about an IF AGC in the ubitx-- use a search engine (or look here in files) to find the Jackal schematic - it has an IF AGC circuit that could be employed, that seems to be derived from the hybrid cascode (W7ZOI) with less stages as I recall.?
I find with an audio filter and audio AGC the ubitx is a decent rig to do some casual HF.? But do explore circuits to your fancy.? Speaking of the hycas, I built one a few years ago - got distracted by our club build of v4 ubitx (that needed some effort to tame) - so I need to think through what band(s) I will deploy the hycas in a receiver.?
73 curt
--
Jack, W8TEE
|
Looking at David's aliexpress listing, it says they are "carbon film".
A google search of "carbon film vs metal film" says metal film is more stable, if that matters.
And says there's lots of variation between manufacturers.
I believe both carbon film and metal film get trimmed to a final resistance value
with a spiral laser trim, adding an inductance that is not defined in the datasheet.
Inductance will vary with batch, depending on how thick the film gets deposited.
So ideally, we would find a quality product, characterize it thoroughly, and stick with it.
Better yet, buy those dummy loads purpose built for microwave frequencies.
Jack's QST article used 3W metal film resistors.
I've used a parallel set of twenty 1K ohm 3W Xicon brand metal film resistors
as a dummy load with good luck.? My nanovna shows a Smith Chart through 30mhz
with a single dot at the center, and still reasonably good at 144mhz.
Most of the inductance shown is likely in the relatively long leads I have.?
Next time I place an order for Tayda or Mouser, I'll buy some 100 ohm 3W resistors
and see what the nanovna thinks of them.? But I suspect they will work well enough.
Regarding the URL:
It's usually possible to strip off their tracking information from these ridiculously long URL's.
In this case, everything from the '?' on out to the end:??
For Amazon, everything from the "/ref" on out to the end.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Sat, Oct 31, 2020 at 10:51 AM, Jack, W8TEE wrote:
If you just use 32966376132 in the Ali search bar, it finds the item.
?
|
David:
If you just use 32966376132 in the Ali search bar, it finds the item.
Jack, W8TEE
On Saturday, October 31, 2020, 1:37:56 PM EDT, N8DAH <dherron@...> wrote:
I have been using these for my dummy loads and they have been pretty darn surprising.
https://www.aliexpress.com/item/32966376132.html?spm=a2g0o.productlist.0.0.1a9e5261YmP5gm&algo_pvid=d2007a98-6b86-4a1d-80ce-61348dbc4deb&algo_expid=d2007a98-6b86-4a1d-80ce-61348dbc4deb-9&btsid=0bb0622d16041657591331983eada4&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
--
David
?N8DAH
-- Jack, W8TEE
|
I have been using these for my dummy loads and they have been pretty darn surprising.
https://www.aliexpress.com/item/32966376132.html?spm=a2g0o.productlist.0.0.1a9e5261YmP5gm&algo_pvid=d2007a98-6b86-4a1d-80ce-61348dbc4deb&algo_expid=d2007a98-6b86-4a1d-80ce-61348dbc4deb-9&btsid=0bb0622d16041657591331983eada4&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
--
David
?N8DAH
|
Good grief...didn't know!
Jack, W8TEE
On Saturday, October 31, 2020, 11:31:38 AM EDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
Yup, this is your thread.
Started two years ago with regard to the QST article.
Jerry, KE7ER
On Sat, Oct 31, 2020 at 08:08 AM, Jack, W8TEE wrote:
We did a similar DL for the November 2018 QST article which also had a watt meter built in. By putting the resistor pack in mineral oil, we were able to run 200W into it for 5 minutes without failure.
-- Jack, W8TEE
|
Gerard
Shirley Dulcey KE1L
Raj vu2zap
Bob Lunsford
MadRadioModder
N8DAH