How Low Pass Filters Work - Ham Radio Q&A

[@buckbrown823]

Very useful and well done video. Both the LPF and a simple ATU, that is at least a line flattener, really clean up the harmonic and out- of-band QRM.

[@slidetbone]

Yes! Joe did a great job! More videos from you and Joe will be great!

[@alexalonso2093]

good information. yes more JOE videos 7 3.

[@MrGhostVortex]

Exactly what I've been looking for! I'd love to get my hand on a set of these, looking to set up a base station on 70cm and I need a bit of filtering.

[@louisseaman8455]

Great voice! I have a filter from years ago that had a few variable capacitors as well, where the tuning adjustment knob came through the case of the TVI filter, making up a 5th or 6th order filter I believe. Keep up the good work.

[@whitefordpipeshandmadebymi7238]

I always used to use a low pass filter but now I have a batter understanding of how they work thanks 😊 CB days a “ Taylor “ filter was popular here in Canada 🇨🇦 but I hated all the adjustments so I opted for the Bencher YA-1 I think it was ? Take care 73 de ve3hip in welland Ontario Canada 🇨🇦

[@mcnugget91]

Michael, glad your demise was not real! Joe was very informative and did great on the video!

[@Andy2e0ree]

Joe did a great job

[@davidsradioroom9678]

I agree.

[@kevinknight7638]

Excellent job , informative and interesting!!

[@josealfredocuevas]

I know this video is 2 years old for a few years old, but I was wondering does the low pass filter work for unwanted RF high levels of static and RF noise coming into my radio? I'm not having an issue with neighbors or getting into any components in the house my issue is I'm receiving about 5 to 7s units of high static level and it seems to be worse on the lower channels, lower frequencies will the low pass filter help reduce some of that noise? KD9MFT

[@John-jn2lw]

"Now we can watch Jackie Gleason while we eat!" Some of the best movies ever made.

[@1fanger888]

Good job guys, thanks

[@EricFullwood]

Great Job, Joe. GoPackGo

[@vtradio]

Does a low pass filter help with harmonics from an old tube transmitter? For example, using a 7.030 crystal? Would it cut down on interference on 14.060, 21.090, 28.120? 73 Paul AA1SU

[@KB9VBRAntennas]

A low pass filter won't help. But if you put a 40 meter band pass filter on the tube transmitter, the spurs at 14.060, 21.090. and 28.120 will be filtered out.

[@mikemcdonald5147]

good info from Joe would love to see more from him. is a low pass filter the same as a band pass filter that dx engineering sells?

[@KB9VBRAntennas]

A band pass filter is slightly different than a low pass filter. Low pass filters either pass or attenuate a broad range of frequencies. For example: a low pass filter will attenuate frequencies above 30 Mhz and pass frequencies below 30 Mhz. A band pass filter will pass a narrow range of frequencies and attenuate all others. A couple examples would be a filter that passes only frequencies in the 20 meter band or a certain 2 meter frequency. Common applications for band pass filters are situations where you are running transmitters on multiple bands and you don't want them to interfere; like at a repeater site. The band pass may be set to allow the repeater frequency to pass- reducing interference from nearby transmitters. Another use would be if you are running a station on 20 meters and another person is simultaneously on 40 meters. This is common on special event stations or field day. Stations can use band pass filters to keep each from interfering.

[@shizzle666440]

What's your thoughts on how near the radio the low pass filter should be. I've read a few threads and some people recommend the patch cable should be as short as possible, while others say they mount it directly to the radio using a double male PL259 barrel adapter.

[@KB9VBRAntennas]

I can see the reasons why you may want to directly connect the low pass filter to the UHF connection on the back of the rig, but I think that's a lot of weight to hang off the antenna jack. I'd use a short piece of coax.

[@dennisweisenreider7314]

Can a lpf be used on the receive side of a uhf repeater? For example if you live near 600/900 mhz cell towers. Please and thank you . D

[@herchellee8639]

Please do a review about AMSAT thank you and 73

[@johnbrown7538]

Yep Michael Pls do a video about amateur satellite

[@KB9VBRAntennas]

That's a great idea- Joe is playing around with some satellite communication so I'll talk to him to see if we can put together a video before it gets too cold outside.

[@cartert5915]

Hey KB9VBR! I Really want to buy a ICOM IC-718 but i have a question. i don't know what what power supply i should get for the radio. if you could let me know that would be great!

[@KB9VBRAntennas]

I'd recommend a 25amp power supply for the Icom IC-718. 13.8v switching power supplies are lightweight and inexpensive. amzn.to/2OGKNF7

[@mattgroat5273]

Nice

[@Dale-wz5yr]

Where do you connect filter at in line? Thanks 73s

[@KB9VBRAntennas]

The filter should be connected as close as possible to the antenna output of the transceiver, before the tuner or any other pieces of equipment.

[@matthewshank73]

Got Bell Industries Transmitter Low Pass Filter C-514-T. Looking at the label-which is the input side from Transmitter? Right or Left side, not labeled. Bought it 1979, can’t remember. thanks Matt N6CUQ

[@africantwin173]

Is the Bencher YA-1 trustworthy.

[@rallypoint1]

Would those 2nd harmonics that an antenna can’t handle and return back to the radio affect a SWR meter resulting in high SWR numbers?

[@chrisazure1624]

When I transmit on 1.25M, it interferes with the TV my wife is watching upstairs. What do I need to resolve this problem. So far, no complaints from the neighbors, but maybe they have not associated it with me.

[@KB9VBRAntennas]

Is it broadcast or cable TV. How much power are your transmitting? Does it interfere at low power? If it's cable, you can try ferrites on the power cord and coax cable.

[@chrisazure1624]

@@KB9VBRAntennas It is broadcast TV and it happens at all power levels of an Alinco 235. I have three ferrite beads on the Coax near the antenna. It is one of your J-Poles, BTW, not that that is the problem. When you say on the power cord, do you mean of the power cord of the TV? Would that need to be near the socket or TV. Do I need Ferrite beads on the receive antenna near the antenna or TV?

[@KB9VBRAntennas]

Thanks for the additional info. Joe and I will be discussing this on the livestream tonight (Jan 7 @ 7pm central) Feel free to tune in and comment in the chat.

[@chrisazure1624]

@@KB9VBRAntennas Knowing how and where to place a pass filter is something I don't understand. Perhaps a picture of one installed is available as a visual guide. Thank you.

[@chrisazure1624]

@@KB9VBRAntennas (Copied from the live stream video for continuity) Thanks, guys. I just put a choke on the antenna wire (a cheap tv antenna) and it is no longer picking up the interference from the 220 transmission. Thanks for the simple fix. I just made several wraps around my fingers and put a velcro strap on to hold it together. It is working fine.

[@Kodo-Nashi]

Wausau!!!

[@bobcrawford5083]

I have issues on 40m inside my home with the tv upstairs when I transmit the tv goes black then comes back on..I do have a low pass filter on my 40m dipole and also my 20m dipole which does not interfere with my tv..I have added snap-on ferrites on my power supply...the coax and the tv cord and also on the cable tv coax..and my swr on 40m is less than 2.0.1 and my tuner takes care of that..none of my ham friends can figure it out either...I even took down my dipole and made another just to be sure..feeling aggravated.....

[@Gordofor12]

Check the grounding on your radio.

[@bobcrawford5083]

@@Gordofor12 Thanks Joe..it has been grounded for years..everything in the shack..this is something that just happened..always something to do as a ham right?..I`ll get it..

[@Gordofor12]

@@bobcrawford5083 I had to wrap our DirecTV receiver in tin foil for 40 meters.

[@bobcrawford5083]

@@Gordofor12 Joe we have comcast..I even put snap on ferrites on the cable before it goes to the TV and also the power strip for TV..tried to do away with power strip just to see..nothing changed..my other flat screen down stairs here I want to switch over and see if that helps...read about these sets are not always compliant with the fcc..onne guy said take off back of set and foil the inside of it..eehh ...I just put together a new dipole a fan 40-20m..tookd down the other and made a new one something has to give....thanks for your vids and input 73..Bob

[@pratwurschtgulasch6662]

if you want to show how a filter works you're doing it wrong with the function generator and oscilloscope, not sure what we are supposed to be looking at. what you want to use instead is either a spectrum analyzer with tracking generator or vector network analyzer. both of those will do a frequency sweep and record the insertion loss. btw. i also looked at that same function generator before and when i saw that it only went up to 30mhz i was like forget about it. instead i bought the FY6900 which goes up to 60 mhz and costs less than half of the siglent. then if you want to generate some real RF look on ebay for cheap RF signal generators for about $50 that go up to like 6 GHz.

[@DonDegidio]

Good info, but you don't want to use one with a radio that has HF + 6M. :-) WB3BJU

[@Gordofor12]

Well if you had a IC756 with two antenna outputs you could put your HF antenna on one and a 6m one on the other then your filter would be just fine on the first one! ;)

[@KB9VBRAntennas]

Or use an antenna switch so your 6 meter antenna isn't inline with the low pass filter

[@earthey7499]

I think I see a TI-30XIIS on the desk! 🙂👍

[@Gordofor12]

Yup!

[@buckfiden9106]

Popular to contrary belief?

[@raysingh5121]

I am the frist fan to wacth

[@radioman6489]

1st