IR type temperature sensors usually give a false reading when pointed to bare metal. At my work where I used to measure like this a lot we always put a small dot of white (typewriter) correction fluid (typex) on the metal for accurate reading. Nice build, it inspires me to get a new life out of a heatpipe type CPU cooler. Although my rigs are QRP…
I really like the simplicity of the system. The 9V battery pack and thermostat sw is so simple it's elegant. I like simple and effective circuits. My compliments.
Thank you for the nice comment. There is always some room for improvement such as using one resistor instead of two. This might give better VHF/UHF SWR performance.
Excellent work! A few notes: - Your NanoVNA was not measuring S11 on the blue curve, but S21. Real return loss would be a bit worse (but that is the same info as SWR, jut presented differently). - Your ground connections might be shorter. I see you connected the pin of the connector to the pin of the resistor with the shortest possible wire, but the ground connection is way longer. I think a similar setup with shorter ground would easily go way further in frequency.
Oh boy, how did I miss that! Sure enough I was on S21 and not S11. The RL did look too good to be true. Thanks OM for pointing that out! I also agree with you about the ground situation. Additionally, I would like to try resistors that do not have the double tabs like I used. Not sure that would help the SWR at VHF/UHF freq's. But the length of the grounds certainily can be addressed. A Part 3 video will be forthcoming after some aforementioned adjustments. 73's
@@rfburns3472 I noticed it because it was a bit too good (1.05 VSWR is -33dB, 1.01 is -46dB, 1.0001 would be around that -90dB. I used an online calculator for those, I only know that 1.5 is around 13dB), and that it did not change at all, even when the SWR got very bad. I'm not that familiar with those resistors (altough a friend of mine also ordered some, might build a similar thing in the future), is the bottom of it also ground? If yes, using a proper 50 ohms feed (maybe on a PCB) it can even go to microwave frequencies. Well, even without that, but I'm not sure.
@@HA7DN After reading your first comment, I changed the return loss from S21 to S11 and got results in line with your online calculator and this conversion chart www.amphenolrf.com/vswr-conversion-chart The bottom flange is NOT grounded. The resistor has two tabs and the flange is "floating". I may replace these with the grounded flange type to see if there is any improvement in the SWR.
Keep in mind: the case and the foil resistor was insulated but it had some capacitence, so when the resistor case is grounded to heatsink and RF connector u have a small capacitor 2 times across the terminal. The 2 peace of 6mm heatpipes is going to dry out from 65-70W and fully dryed-out at 80W heat transporting. U find they act like an empty cooper tube.
Please see my new video Part 3 soon to hit the channel with an improved version of this DL. It has much better performance from 60 MHz to 600 MHz. So far, the heat pipes are doing well but I will keep an eye on them going forward. Thanks!
@@jonathancotner7040 I will demonstrate that in the next Part 3 video where I will also build another DL using a single higher frequency Aneran flanged resistor and Type N connector. Please stay tuned as this might be an interesting improvement at the VHF/UHF frequencies.
Kinda worried about the temperature imbalance between the two resistors. Power should be dividing equally between the two. I have used a single 50 ohm 100 watt resistor on a heat sink that was used in a 450 MHz single stage circulator on a Motorola Micor transmitter. Never had a heating issue since the SWR was alway low and we had decent bandpass cavities on the TX side.
I agree. The two resistors measure 100 ohms and in parallel the dc resistance is exatcly 50 ohms. So, each resistor should dispate the same amount of heat. It could be I was not getting a good placement of the IR gun on each resistor.
Your return loss may be better than 90db, I believe you are maxing out the dynamic range of the nanovna. I've built similar loads but used coaxial cable from the connector to the (single) resistor which was rated up to the ghz at I believe 500w, and managed to get the SWR to an acceptable level all the way through 70cm, but I decided it was too hard to use the coax and a geat sink so I went the cantenna route and used mineral oil. I haven't got a way to put more than 100 watts through it currently, but it takes 100w happily for as long as I'm comfortable keying the radio.
I agree. The dynamic range of the NanoVNA was exceeded and appearing almost too good. I also should have recalibrated the VNA for the 220/440 MHz range and possibly got a better SWR. Your cantenna is a great way to go with your 100 watts.
@@deanberglund2332, you remind me of when I got a job testing spy satellite subassemblies, and each of the 1k pull-up resistors on the board (through-hole days,) had a tiny serial number on it and a 24 hour burn-in thermal curve document, all time annotated, room temperature logged, dated, signed, and stamped with the stamp of the person certifying the results, plus the make, model, and serial number of the piece of equipment that recorded the results for that 1k pull-up resistor. That was when I knew I'd made the big-time in the electronic-test world. :)
Nicely done. I would HIGHLY doubt your ever going to simulate that test in a real world use case though. MOST keydown's to a dummy load are a few seconds at most, when testing.
You are correct. But, there are occasions when transmisions into the dummy load may require some extended time. Let's say I want to run a audio frequency sweep on my AM transmitter. This may require quite a bit of extended key down time. Thanks for your kind words!
@@jspencerg I acknowledged my "mistake" in CC (closed caption). "Whoops! He made a misktake. The return loss was not on S11. It was later measured at -32 dB @ 30 MHz." I am working on a Part 3 video which will display it correctly.
I'm building a similar device. I'm hoping for 200 Watt capability from a single 250 Watt Anaren terminator and a Heatsink. My band of operation is 144 Mhz. I want to reduce the distance from the Ground path of the connector to the body of the Heat sink, I hope this will be better at VHF. Regards Andrew ZL2ALW
Hi Andrew and welcome! From my testing in the video you can see how poorly the DL performs above 60 Mhz. I have come up with a much better design based on what you just stated...reducing the physical distance from the resistor flange to the coaxial connector. SWR is now 1:0:1 from 1 MHz to 220 MHz and 1.1:1 at 450 MHz. Part 3 video coming out this weekend.
That's a very good question. The problem is connecting anything to the resistor termination leads would cause a massive disturbance in the desired impedance. You might have a better chance using a thermoelectric system to transfer heat into electricity. The fan I used with a 9.1 volt battery draws .240 amps. That's 2.2 watts of power.
You might be correct to some degree Jerome. High quality 259/239's are rated to 300 MHz while Type N's are rated to 11 GHz. SPOILER ALERT! Part 3 video will be a TYPE N female connector and a somewhat different construction arrangement.
Nice! Where did you source the resistors? If you short the outer conductor of the coax jack to ground with another couple of short solder wick you even might improve the SWR properties.
I just added the source for resistors and CPU heat sink in the "description". I believe you are correct that adding the solder wick will improve the SWR. Standby for that change in video Part 3.
Thank you! It's a HP desktop CPU fan from eBay. www.ebay.com/itm/155725388653?epid=16019326502&itmmeta=01J4A7VFB81Y6JG9Y2WPMBKV2X&hash=item2441f4db6d:g:UW0AAOSwAkpk35kT&itmprp=enc%3AAQAJAAAAwPqwypUvCxpBPw%2BrJ47ipAppoGxF5B8PR3pQeFbSZslJh0c7oSDOa8He2VOZNlnHtsVzX9Us59x%2F8E4h%2F5wsTvor8w8MnmnMAtlSwrsQMijsrnEv0Y0R9XsjfJrPgjqGAs%2BC%2FbVisrqnfk%2FNFqm6QIH8Zhjjkf99xDnmXSZMko6Uk9P2tyoWTE5xxzwX8kYa9Ys5PMGJby3GuAH3fbAUAwtRqnyI6W5wPi9fqd9D32bXf%2Fvg2UNa%2FXrIyYbyeeCqog%3D%3D%7Ctkp%3ABk9SR-r17ceiZA
Can you please tell us what the values of your resistors are? Part number etc. Thank you for an exciting video. Oh, I see you described it in part 1. Thanks anyway..
@@rfburns3472 Thanks again. Great video. I think I'm gonna try this build too. Possibly propose this as a project for our Build a Thon we have monthly at our ham radio club.
@@deanberglund2332 You might want to wait a bit as I am building up what I think will be an improved verison of this DL. The same type CPU heat sink/fan will be utilized with a much better UHF/VHF resistor. I should have the parts in a few days and will have the Part 3 video published up soon. Thanks for watching!
@@rfburns3472 Thanks for the heads up but I already ordered the resistors. They aren't that expensive so not all is lost. I will try to wait till you come out with Part 3 to see what happens. Thanks again. 👍
IR type temperature sensors usually give a false reading when pointed to bare metal. At my work where I used to measure like this a lot we always put a small dot of white (typewriter) correction fluid (typex) on the metal for accurate reading.
Nice build, it inspires me to get a new life out of a heatpipe type CPU cooler. Although my rigs are QRP…
Go for it Robert! And, thanks for the tip on IR false readings.
I don't understand the RF info much, but I can see you put a lot of effort into making that, and it looks very professional.
Thank you so much for the complement!
Neat idea, a lot more compact and clean than a bucket of oil. Fan will perform better on the full 12V.
100% agree and I will test the fan with 12V in the next Part 3 video.
I really like the simplicity of the system. The 9V battery pack and thermostat sw is so simple it's elegant. I like simple and effective circuits. My compliments.
Thank you kindly John. I have a new improved version coming out soon in Part 3. Maybe in a week or so.
Very nicely done, looks great.
Thank you. I appreciate your kind comment!
That looks Good. All the important stuff was addressed.
Thank you for the nice comment. There is always some room for improvement such as using one resistor instead of two. This might give better VHF/UHF SWR performance.
Excellent work!
A few notes:
- Your NanoVNA was not measuring S11 on the blue curve, but S21. Real return loss would be a bit worse (but that is the same info as SWR, jut presented differently).
- Your ground connections might be shorter. I see you connected the pin of the connector to the pin of the resistor with the shortest possible wire, but the ground connection is way longer. I think a similar setup with shorter ground would easily go way further in frequency.
Oh boy, how did I miss that! Sure enough I was on S21 and not S11. The RL did look too good to be true. Thanks OM for pointing that out!
I also agree with you about the ground situation. Additionally, I would like to try resistors that do not have the double tabs like I used. Not sure that would help the SWR at VHF/UHF freq's. But the length of the grounds certainily can be addressed. A Part 3 video will be forthcoming after some aforementioned adjustments. 73's
@@rfburns3472 I noticed it because it was a bit too good (1.05 VSWR is -33dB, 1.01 is -46dB, 1.0001 would be around that -90dB. I used an online calculator for those, I only know that 1.5 is around 13dB), and that it did not change at all, even when the SWR got very bad.
I'm not that familiar with those resistors (altough a friend of mine also ordered some, might build a similar thing in the future), is the bottom of it also ground? If yes, using a proper 50 ohms feed (maybe on a PCB) it can even go to microwave frequencies. Well, even without that, but I'm not sure.
@@rfburns3472 I'd enjoy seeing a part 3 video when it comes out. Thanks.
@@deanberglund2332 It's in the works....thanks!
@@HA7DN After reading your first comment, I changed the return loss from S21 to S11 and got results in line with your online calculator and this conversion chart www.amphenolrf.com/vswr-conversion-chart
The bottom flange is NOT grounded. The resistor has two tabs and the flange is "floating". I may replace these with the grounded flange type to see if there is any improvement in the SWR.
Keep in mind: the case and the foil resistor was insulated but it had some capacitence, so when the resistor case is grounded to heatsink and RF connector u have a small capacitor 2 times across the terminal.
The 2 peace of 6mm heatpipes is going to dry out from 65-70W and fully dryed-out at 80W heat transporting. U find they act like an empty cooper tube.
Please see my new video Part 3 soon to hit the channel with an improved version of this DL. It has much better performance from 60 MHz to 600 MHz.
So far, the heat pipes are doing well but I will keep an eye on them going forward. Thanks!
Please note I should have recalibrated the VNA when testing the 144/220/440 MHz SWR. This may have resulted in a lower SWR for these bands.
I came here to say that.
And I'd enjoy a follow up video with it calibrated
@@jonathancotner7040 I will demonstrate that in the next Part 3 video where I will also build another DL using a single higher frequency Aneran flanged resistor and Type N connector. Please stay tuned as this might be an interesting improvement at the VHF/UHF frequencies.
@@jonathancotner7040 And you would be correct! Thanks
Kinda worried about the temperature imbalance between the two resistors. Power should be dividing equally between the two. I have used a single 50 ohm 100 watt resistor on a heat sink that was used in a 450 MHz single stage circulator on a Motorola Micor transmitter. Never had a heating issue since the SWR was alway low and we had decent bandpass cavities on the TX side.
I agree. The two resistors measure 100 ohms and in parallel the dc resistance is exatcly 50 ohms. So, each resistor should dispate the same amount of heat. It could be I was not getting a good placement of the IR gun on each resistor.
Your return loss may be better than 90db, I believe you are maxing out the dynamic range of the nanovna. I've built similar loads but used coaxial cable from the connector to the (single) resistor which was rated up to the ghz at I believe 500w, and managed to get the SWR to an acceptable level all the way through 70cm, but I decided it was too hard to use the coax and a geat sink so I went the cantenna route and used mineral oil. I haven't got a way to put more than 100 watts through it currently, but it takes 100w happily for as long as I'm comfortable keying the radio.
I agree. The dynamic range of the NanoVNA was exceeded and appearing almost too good.
I also should have recalibrated the VNA for the 220/440 MHz range and possibly got a better SWR.
Your cantenna is a great way to go with your 100 watts.
nice and simple build. Can u please post the serialnumber of the tempswitch (varistor)?
Thank you! I got these on eBay....Normally Open Thermal Switch Temperature Sensor Thermostat KSD-01F 50
I'd be happy with just the part number. :)
@@deanberglund2332 I added it in the "Description".
@@deanberglund2332, you remind me of when I got a job testing spy satellite subassemblies, and each of the 1k pull-up resistors on the board (through-hole days,) had a tiny serial number on it and a 24 hour burn-in thermal curve document, all time annotated, room temperature logged, dated, signed, and stamped with the stamp of the person certifying the results, plus the make, model, and serial number of the piece of equipment that recorded the results for that 1k pull-up resistor. That was when I knew I'd made the big-time in the electronic-test world. :)
@@johnwest7993 Awesome and productive post. I'm sure you feel better about yourself now. :)
Nicely done. I would HIGHLY doubt your ever going to simulate that test in a real world use case though. MOST keydown's to a dummy load are a few seconds at most, when testing.
You are correct. But, there are occasions when transmisions into the dummy load may require some extended time. Let's say I want to run a audio frequency sweep on my AM transmitter. This may require quite a bit of extended key down time. Thanks for your kind words!
@@rfburns3472 You should redo the video. The s21 for s11 mistake is terrible.
@@jspencerg I acknowledged my "mistake" in CC (closed caption).
"Whoops! He made a misktake. The return loss was not on S11. It was later measured at -32 dB @ 30 MHz." I am working on a Part 3 video which will display it correctly.
I'm building a similar device. I'm hoping for 200 Watt capability from a single 250 Watt Anaren terminator and a Heatsink. My band of operation is 144 Mhz. I want to reduce the distance from the Ground path of the connector to the body of the Heat sink, I hope this will be better at VHF. Regards Andrew ZL2ALW
Hi Andrew and welcome!
From my testing in the video you can see how poorly the DL performs above 60 Mhz.
I have come up with a much better design based on what you just stated...reducing the physical distance from the resistor flange to the coaxial connector. SWR is now 1:0:1 from 1 MHz to 220 MHz and 1.1:1 at 450 MHz. Part 3 video coming out this weekend.
Is there some way that you could power the fan from the incoming RF energy? it seems like that would be very cool.
That's a very good question.
The problem is connecting anything to the resistor termination leads would cause a massive disturbance in the desired impedance. You might have a better chance using a thermoelectric system to transfer heat into electricity. The fan I used with a 9.1 volt battery draws .240 amps. That's 2.2 watts of power.
I'm betting that the badness around 450MHz is mostly due to that PL259-SO239 combo. Wonder how it would do with an N connector?
You might be correct to some degree Jerome. High quality 259/239's are rated to 300 MHz while Type N's are rated to 11 GHz. SPOILER ALERT! Part 3 video will be a TYPE N female connector and a somewhat different construction arrangement.
Nice! Where did you source the resistors?
If you short the outer conductor of the coax jack to ground with another couple of short solder wick you even might improve the SWR properties.
I just added the source for resistors and CPU heat sink in the "description".
I believe you are correct that adding the solder wick will improve the SWR. Standby for that change in video Part 3.
Is that an xbox 360 cpu heat sink? Wonderful
Thank you! It's a HP desktop CPU fan from eBay.
www.ebay.com/itm/155725388653?epid=16019326502&itmmeta=01J4A7VFB81Y6JG9Y2WPMBKV2X&hash=item2441f4db6d:g:UW0AAOSwAkpk35kT&itmprp=enc%3AAQAJAAAAwPqwypUvCxpBPw%2BrJ47ipAppoGxF5B8PR3pQeFbSZslJh0c7oSDOa8He2VOZNlnHtsVzX9Us59x%2F8E4h%2F5wsTvor8w8MnmnMAtlSwrsQMijsrnEv0Y0R9XsjfJrPgjqGAs%2BC%2FbVisrqnfk%2FNFqm6QIH8Zhjjkf99xDnmXSZMko6Uk9P2tyoWTE5xxzwX8kYa9Ys5PMGJby3GuAH3fbAUAwtRqnyI6W5wPi9fqd9D32bXf%2Fvg2UNa%2FXrIyYbyeeCqog%3D%3D%7Ctkp%3ABk9SR-r17ceiZA
Can you please tell us what the values of your resistors are? Part number etc. Thank you for an exciting video. Oh, I see you described it in part 1. Thanks anyway..
I placed the parts info in the "Description" in both video's. Thanks for your nice comment!
@@rfburns3472 Thanks again. Great video. I think I'm gonna try this build too. Possibly propose this as a project for our Build a Thon we have monthly at our ham radio club.
@@deanberglund2332 You might want to wait a bit as I am building up what I think will be an improved verison of this DL. The same type CPU heat sink/fan will be utilized with a much better UHF/VHF resistor. I should have the parts in a few days and will have the Part 3 video published up soon. Thanks for watching!
@@rfburns3472 Thanks for the heads up but I already ordered the resistors. They aren't that expensive so not all is lost. I will try to wait till you come out with Part 3 to see what happens. Thanks again. 👍
@@deanberglund2332 Your welcome Dean and hope to get that video up next week or so.
73's🎙KD9OAM🎧
73's