Low VHF interference

rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
here are my rf 4 and rf 6. rf 4 comes in great all the time cause its close by. rf 6 abc comes in about 70% of the time
View attachment 147046 View attachment 147047
Thank you for the report and the new images. I notice that you have set the gain at max for all signals. It should be reduced for strong signals to show the greatest SNR with the strongest shown signal. More is not always better. Please experiment with the gain setting.

In this video, I started with the gain at minimum, went all the way up to max gain, and then down to about halfway at 28dB. It takes a long time to download; it goes from full width to half width when ready.
https://www.dropbox.com/s/w62g62araggzy9e/SDR# v1.0.0.1732 - RTL-SDR (USB) 2020-08-16 20-02-32.mp4?dl=0
 
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freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
Thank you for the report and the new images. I notice that you have set the gain at max for all signals. It should be reduced for strong signals to show the greatest SNR with the strongest shown signal. More is not always better. Please experiment with the gain setting.

In this video, I started with the gain at minimum, went all the way up to max gain, and then down to about halfway at 28dB. It takes a long time to download; it goes from full width to half width when ready.
https://www.dropbox.com/s/w62g62araggzy9e/SDR# v1.0.0.1732 - RTL-SDR (USB) 2020-08-16 20-02-32.mp4?dl=0
Thanks rabbit73 for the video, i will try lower the gain to see what happens later on today. thanks again
 

freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
Thank you for the report and the new images. I notice that you have set the gain at max for all signals. It should be reduced for strong signals to show the greatest SNR with the strongest shown signal. More is not always better. Please experiment with the gain setting.

In this video, I started with the gain at minimum, went all the way up to max gain, and then down to about halfway at 28dB. It takes a long time to download; it goes from full width to half width when ready.
https://www.dropbox.com/s/w62g62araggzy9e/SDR# v1.0.0.1732 - RTL-SDR (USB) 2020-08-16 20-02-32.mp4?dl=0
GM. here are 2 screen shots of channel 4 and 6 with gain lowered. my gain was around 20db before the noise started to in crease. channel 2 wasnt coming in.
6 adjusted gain.jpg 4 adjusted gain.jpg
 
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rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
GM. here are 2 screen shots of channel 4 and 6 with gain lowered. my gain was around 20db before the noise started to in crease. channel 2 wasnt coming in.
View attachment 147084 View attachment 147083
Thank you for the excellent images! Your technique is perfect. Must be because you are a Jersey guy. I grew up in a small town between New Brunswick and Perth Amboy. My family had a summer cottage on the Jersey Shore inland from Mantoloking.

The SNRs shown in the images are consistent with your reception descriptions.

freeisformeSatGuysCH4 adjusted gain2.jpg

freeisformeSatGuysCH6 adjusted gain2.jpg
 

freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
Thank you for the excellent images! Your technique is perfect. Must be because you are a Jersey guy. I grew up in a small town between New Brunswick and Perth Amboy. My family had a summer cottage on the Jersey Shore inland from Mantoloking.

The SNRs shown in the images are consistent with your reception descriptions.

View attachment 147095
View attachment 147096
Thanks rabbit73. im north of Atlantic city along the coast. i peaked the channel, if i went higher with the gain the noise floor would increase.
 

freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
rabbit73 here is channel 2 from Thursday morning. it would be nice if i was able to receive the channel this good all the time. i also was receving ( not watchable) WJLP out of Middletown NJ too.
2 adjusted gain.jpg
 
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rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
rabbit73 here is channel 2 from Thursday morning. it would be nice if i was able to receive the channel this good all the time. i also was receving ( not watchable) WJLP out of Middletown NJ too.
View attachment 147126
That channel 2 signal looks good. I suspect that the difference between a good day for channel 2 and a bad day for channel 2 is the local noise level. Is it worse at certain times of day?
 

freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
local interference. i agree. i kinda would like to track down the interference but i learned how difficult it would so i just let it go.
 

freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
rabbit3: there is s question i asked that didnt get answered. at the time was for rf channel 6. why would the antenna have to be at the 8 oclock and 4 oclock position for rf channel 2? rf channel 6 antenna needs to be at the 9oclock and 6 oclock position made of twin lead too. i will take a picture when the attic is not hot. thanks
 

rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
rabbit73 i dont like heights much 95 ft high antenna. no thank you. lol. the graphs are ver interesting. thanks you
I don't like heights for me, but they can be good for an antenna.:)

The software that I used for the second profile gives the elevation for a location, which is the height of your ground above sea level. It then allows me to add the height of your antenna above your ground level.
75 ft above sea level + 20 ft above ground level = 95 ft above sea level for antenna
 

rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
rabbit3: there is s question i asked that didnt get answered. at the time was for rf channel 6. why would the antenna have to be at the 8 oclock and 4 oclock position for rf channel 2? rf channel 6 antenna needs to be at the 9oclock and 6 oclock position made of twin lead too. i will take a picture when the attic is not hot. thanks
I can't find where you asked that question. Is it in this thread?

I don't quite understand your oclock references for an antenna. Are you talking about what the antenna looks like from above, or at eye level?

Looking at a dipole antenna from above, it is bi-directional. So, it should be aimed broadside (perpendicular) to the transmitter:

Dipole Pattern 3.png


This is what my CH 3 indoor folded dipole looks like. It is 14 gauge wire on yardsticks:

CH3 Indoor Folded Dipole.jpg


CH3rcvFDant2.jpg
ThorCH33to3Cant-8dBmV.jpg

Thor33-3Ant-8dBmVtoTV_SNRrev.jpg
 
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rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
rabbit73: there is s question i asked that didnt get answered. at the time was for rf channel 6. why would the antenna have to be at the 8 oclock and 4 oclock position for rf channel 2? rf channel 6 antenna needs to be at the 9oclock and 6 oclock position made of twin lead too. i will take a picture when the attic is not hot. thanks
Is this what you mean by a channel 6 question?

Your other thread:
KJWP Philadelphia reception help
..... Also i have a twin lead antenna for WPVI, that is vertical and aluminum window screen as a reflector about 36 inches back, i get zero signal placed horizontal...... also i have residential power lines 30 feet from the antenna and at the same height. i have a 32 inch lcd up in the attice with me, the antenna is connected to the converter box " to get the signal meter" and then the tv.
It is possible that the power line is blocking the horizontally polarized portion of their circular polarized signal; only the vertically polarized portion can get through.
RabbitEars.Info

freeisformeSatGuysCH6CircularPol.JPG


They also have an application in for 56 kW horizontal only; I doubt that it will be granted. If it is, your reception of WPVI might get worse.

Their Auxiliary transmitter is 32 kW horizontal only.
 
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freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
My folded twin lead is a JOKE compared to your. I cant tell time in time last message too. In a stright line, one end is at the 10 oclock and the other end is at 4 oclock for channel 2. Im not horizontal.
 

freeisforme

Thread Starter
SatelliteGuys Guru
Feb 21, 2017
123
20
south jersey
With the power lines and signal reflections in the attic, you should put your antennas in whatever position and location gives you the best reception.
that what i did. it was a pain. would it make any difference if i make a new twin lead out of 12 or 14 awg wire like yours? thank you
 

rabbit73

Well-Known SatelliteGuys Member
Jul 17, 2020
29
25
S.E. VA
that what i did. it was a pain. would it make any difference if i make a new twin lead out of 12 or 14 awg wire like yours? thank you
When you make a folded dipole, you cut it to the right length for a certain channel. It will work best for that channel and will pickup other channels, but not quite as well. If you use a larger diameter wire, it will pick up the other channels better; we call that greater bandwidth.

If you use a larger diameter wire, it is difficult to say how much better the other channels will be, but the general rule is the larger the diameter, the greater the bandwidth.

Good twinlead comes with 18 gauge wire, but most is 20 gauge. Cheap FM folded dipole antennas use 30 gauge twinlead.

PET10-8110feedpoint.jpg

PET10-8110twinlead.jpg

I use 14 gauge THHN
CH3 Indoor Folded Dipole5_1.jpg


One inch diameter copper tubing would be the best, but I don't think it is worth the trouble and expense.
 
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