Hi, I just wanted to thank you, because your video was helpful for some details for a paper about filtration. So, thanks.

Jim, Thanks for your great videos and patient instruction.Really Great!

Hi Jim, Just got my Rigol this week...and wnat to know how the show loss in dB's as you've shown. this si obviously pretty important when you are looking at a cavity device. Tuned a bunch of cavities and duplexers i had laying around and it did a great job....but I still would like to know the degree of loss (in dB's). Also....not very ggod directions on the Rigol....so i'm flying blind. Thank God for guys like you, and others who are leading the blind.

The DSA-815 has leakage internally from the Tracking Generator (TG) to the Spectrum Analyzer input. Thus it will not display notches that are deeper than whatever this leakage level is for your particular unit. I've covered this in other videos in this series. In most cases the deepest notch that can be displayed will be in the neighborhood of -90 dBc(dB below carrier). With the tracking generator turned off an external signal generator can be substituted for the TG as a signal source then notch depths greater than -90 dBc should be possible to confirm. One can estimate the depth by looking at the -90 dBc levels displayed above and below the desired notch frequency then noting the slope of the trace and estimating what the actual depth must be half way between these two points.

@ehsnils

6 жыл бұрын

From what I can deduce the DSA-815 with a tracking generator is probably one of the better price/performance alternatives when it comes to tuning filters for 2-way radios. There are probably better performing instruments out there, but this will do the job at a price that at least some of us can afford.

There are instruction for making cavity filters on the internet as well as in ARRL and probably RSGB repeater books but the unit shown in the video is a commercial unit (Telewave). There is a lot of machining and specialized components required to make a cavity filter.

Hi Jim, Nice to have found such useful videos. That has made very smooth and versatile the use of my spectrum analyzers. I just got a small problem in normalizing my Willtek 9102 and unfortunately there are not many app notes or else to make it better but we shall learn. All the best Rob 9J2RD

4:35 LOL don't forget to set the clutch on the drill-driver to its loosest setting.

As for tuning a two connector notch-only filter, it would depend on whose unit you are tuning and what their directions are for tuning them. Normalization would involve connecting your test cables together with an "N" barrel, Normalize the Rigol, then connect the cavity between cables where the barrel was in exactly the same way that a Band Pass Cavity Filter is tested. The "N" Barrel provides a 0dB reference and the notch depth and loss of the notch filter will be easily determined this way.

Thank you sir, very informative.

Many Thanks Sir for your explanation, 73's From PJ2SM

Settings are: RBW=30kHz, VBW=Auto(30kHz), Tracking Generator=0dBm, Start 140MHz, Stop 150MHz (you could get better results using a 1MHz Span, potentially), TG Normalized to remove level variations and to set reference to 0dB, and Sweep=Auto. This should provide roughly 80dB dynamic range. Each cavity should be individually tuned for the Pass/Reject pair that you want then cabled together for final 'tweaks'. I don't provide cable lengths. This varies by Mfg. I hope this helps.

Very nice and informative videos, well done keep them coming:) 73's Ray 9H1RA

Thank you very much for these informative videos! I really learned a lot! David, N5GEB

thank u for the useful information

you can make a video showing adjustment and read 4 cavities together ?

Hi mr Jim, very informative video! could you try to reverse the cables - the input on the output and the output to the input to check if they still have same matching?

Perhaps the Invar tuning rod is firmly attached near the end of the moveable sliding center conductor, so the length precisely follows the Invar rod? It wouldn't drift much then. But to build a unit for Ham purposes is difficult due to sourcing the Invar rod at reasonable cost ...

Hi Jim... great vids! I have a celwave 526 BpBr duplexer spec'd to notch down to -100Dbm. For some reason, no matter what settings I use, I cannot get the Rigol to read more than -90 or so Dbm !!! What could I be doing wrong... everything else looks fine to me and the wave form matches the spec sheet... just won't go down to -100!! Thanks Dave

What length of cable did you use for the pass/reject cavity and how did you determine this length?

Thanks for the great video. Since you work at Telewave, could you please show the proper tuning of a BP-BR 4 or 6 cavity duplexer using the DSA815-TG? That would be very useful for the Amateur Radio community. I know the BP and BR tuning would be similar to your notch and BP demo, but it would be interesting to see the interaction between the cavities and the peak and notch adjustments. Keep up the great work. Thanks again, and 7 3 Dave, K7DMK

its kinda funny why the freq goes up when the plunger goes in, is the plunger actually shortening when going in?

which cable lengths size recommended to use of 144 - 174 MHz and 433 - 440 mhz for rigol dsa815-tg

I would like to build one, is to give me the project?

Great video. Very interesting. Barry, KU3X

hello,73's,id like to know what is the setting when you doing this alignment? i have a duplexer need to align on amateur band,its a Sinclair Q2220e..Tnx..

could pass the measures of the stub? ..

I have been trying to use HP8920B Communication test set to test bandpass cavity filter, but unfortunately, I am unable to do it. Do you have any idea how to set it up and use HP8920B to test the bandpass cavity filter, James? I would appreciate your help very much.

@BMWGSA

7 жыл бұрын

contact me if you still having troubles with 8920

Jim, could you expand just a bit on the thermal design? You mention that the tuning rod cancels out center conductor expansion. Both aluminum and copper have near +10 micro inches growth per inch per degree F. To offset this you would need a metal with a negative temperature coefficient, say -10. Invar nears +1 but I can find none which are negative.

@jimeagle1

7 жыл бұрын

Chris Scott You bring up a good point. I am not a cavity filter designer and I was only repeating what I was told about the reason for use of the Invar. However the use of +1 material with +10 material would still cut any temperature related detuning in half. By the way, generally there is also a small value capacitor used in many cavity combiners and/or duplexers and these can certainly have negative temperature coefficients. Are there any cavity designers out there who like to enlighten us on this subject?

Hello Sir, I have made a set of band pass filters but now I have put a capacitor to made this filters notch filters. My question is are the RX and TX notch filters the same? how can I let the high frequency pass and reject the low frequency and how do I let the low frequency pass and reject the high frequency? I have made all 4 identical. thank you for your reply! 73's from PJ2SM

@jimeagle1

6 жыл бұрын

Sergio Mackay There will be a notch both above and below the main peak response for most duplexers. Use a wide and sweep (10 MHz or more) to find the lower (or higher) notch. Readjust Main peak tuning and Notch tuning in order to notch below or above the peak response. If you cannot get the desired Peak / Notch relationship you might need to adjust the loop size. You might want to check out videos at Telewave.com for further instructions about duplexer tuning. There are also several videos on KZread about tuning up duplexers.

Hello James I'm Sergio Mackay PJ2SM, I have make 6 duplexers (notch filters) 3 for TX and 3 for RX, I get between 21 and 27 db notch only on each one, but should be enough for me if I get 75 db , when i put 2 together I get about 50 db notch, but when I put the 3 th one it stay about 50 db, my question is WHY, i don't get more db's? p.s I have about 0.4/0.6 db insertion loss on each one.

Hello James, I enjoyed your video. I have some Telewave bandpass filters. Is there a simple way to convert them to Band pass / band reject?

@jimeagle1

2 жыл бұрын

If you had the correct Pass-Reject loop for the can, it is fairly simple. However, it also requires a special can top to allow for the required anti-resonant tuning cap. It might be possible to get this done by Telewave but I haven't worked there for a number of years thus don't know their current policies.

@crimson0arrow

2 жыл бұрын

@@jimeagle1 Thank you for the quick reply James. Unfortunately I know little about Cavities. For the Pass-Reject loop does it have to go inside the can or attach to the connector at the top? Same for the anti-resonating tuning cap? Finally could please point me to where I might get the construction details.

@jimeagle1

2 жыл бұрын

As I indicated, this isn't really something that can be "homebrewed". The factory might do it for a price but it takes significant changes to the top of the unit and the loop inside. Best done at the factory.

Need a decibal product db-4050 bpbr tuned in my work shop. I'm located in the north side of Chicago. Willing to pay someone for there time!!! let me know. Thanks

me indicates some project to 2M? ..?

"hello david where I can buy this equipment I'm from peru" Contact Rigol North America. They may be able to assist you. (I'm not Dave (EEVBlog), by the way. My name is Jim.) Contacto Rigol América del Norte. Ellos pueden ser capaces de ayudarle. (No estoy de Dave (EEVBlog), por cierto. Mi nombre es Jim.)

👍🏻👍🏻 THANK YOU!! 73. KD2MKZ

The DSA 815 has very high mistake in the amplitude.

@jimeagle1

9 жыл бұрын

Please explain what you mean by a 'very high mistake in the amplitude'. I have not found this to be true when using the Normalize mode with a SPAN that is as narrow as practical to show both the peak and null of a cavity. One does need to use the Accy sweep mode to ensure frequency accuracy and appropriate RBW, VBW, and Sweep speeds to achieve proper results just like any other Spectrum Analyzer.

@ElmshornBoy

9 жыл бұрын

James Eagleson In the Hamburg University of Applied Sciences is a lab for communication technology. My group did a simple Amplitude Modulation. On the scope screen we saw modulation factor about 50%. The Rigol DSA 815 showed 39,99%. I tried to find the mistake in my messuring, however, the mistake is to find in the technical data. Amplitude is shown inaccurate by bigger than 1,5 dB / dBm. The difference explained why the scope had shown verything right and the loss of 10% apmlitude at the Rigol. So 10% is many if inaccurate amplitude shoulbd be below 5%.

@jimeagle1

9 жыл бұрын

ElmshornBoy Were you using the Rigol in the Linear mode or Log Linear mode?

@jimeagle1

9 жыл бұрын

ElmshornBoy Yes, there does appear to be a discrepancy in the Zero Span, Linear Scale representation on the screen of the Rigol DSA815. It shows the bottom of the modulation at about 40% when peak modulation is shown at 100%. Thus I am not certain what Rigol's Percentage scale is trying to show us. If I use the Peak Table with a dBm Log reference, the carrier falls at -0.03dBm and each sideband falls at -12.03dBm just as I would expect for 50% modulation. At the same time the DSA815 Percent scale shows each sideband at 25% when the carrier is set to 100% which appears to be measuring percent of power in each sideband (i.e. 25% power in each sideband for a total of 50% modulation, which is the correct answer). It is unclear what Rigol is trying to represent by their 100% reference when the unit is placed in wide bandwidth (example 20kHz RBW), Zero Span, and Linear modes. It does not appear to be modulation depth, however.

@ElmshornBoy

9 жыл бұрын

Ma!ny thanks! I was a pleasure to tlak with such an competent and experienced Engineer. :-)

Cool video! If ya get a sec you should check out one of ours! Hope you like it!