Does the discone need to be grounded? i googled it and it say''s it doesn't have to be is that true?
What antenna configuration do i use?
A Discone works independent of any ground. However, if its mounted outside you should ground the mast and feed line to NEC specs for safety.
ok .... maybe you can answer this question i asked earlier but didn't get a answer... If i run 40 foot of RG6 and go into a splitter can i use RG58 pigtails to connect my dongles to the splitter or will that defeat the purpoose of the RG6?
Also i found this dsdtune what exactly does that do? i'm using dsdplus fastlane and i love it i still got some learning to do like for example i am listening to a NXDN48 CB channel and i'm wondering if that is a trunked channel because i read that in order to hear NXDN you have to set it up in the frequencies file i'm just not real sure how that is done.
I'm kind of an RF purest and don't mix 50 ohm and 75 ohm cables or components in a system. I would rather see 40ft of RG-8 or LMR400 feeding at the most a 2-way 50 ohm splitter then you can use short runs of 50 ohm RG-58 to the receivers. A 2-way splitter will loose at least 50% of the signal and a 4-way will loose 75% or more of the signal unless you make up for it with a low noise, high level preamp in front of the splitter. Or get an active multi coupler like a Stridsberg which works fine for most users.
Yeah but my problem is i'm using 4 RTL-SDR dongles so in order to use them i have to use a 4 way splitter i do have a noolec LNA at the antenna.
So using short runs of rg58 to connect the dongles to the splitter and rg6 going out to the antenna will not defeat the purpose of the rg6? i don't want to buy rg6 if my rg58 pigtails are gonna cancel out the rg6 ya know?.
Yes, the cable type have F male on one end, female on the other. there are UHF, BNC, and N types available.
I can only relate by example.
My discone is on the roof 2 stories, LMR-400, 65 foot into an FM trap, then 15 DB preamp. That feeds a 4 way splitter with one split to my scanner, one to my SDR, one to my TV. The TV works fine right off the sp;itter but for my scanner, I have a 20 Db attenuator.
For my SDR I have 10 Db attenuator. that fed with LMR 140 pigtail with SMA connectors. so I have a couple Db gain into the SDR.
With SDR #r, if I leave AGC on, signals and noise are just too hot, so I keep the gain at about 8 to 14 Db.
I still get a couple hot signals on VHF like S9. UHF, I run gain about 10 to 18 Db. with that, I can pick up a ham repeater 35 miles away.
For my scanner, this is still too hot for it, so looking at 25 to 30 Db attenuator.
Those won't cancel anything. RG6 is very common for runs to antennas and then RG58 pigtails to dongles are common.
Or maybe RG-174
Why not do things right and build out either a 50 ohm system or a 75 ohm system? Pick one and keep all components and cables compatible. You can buy very thin 75 ohm cables with F connectors already installed to use from a splitter to the radios to keep everything 75 ohm. RG-179 is a 75 ohm version of silver/Teflon RG-316 and much thinner, more flexible than RG-58. If your LNA is on the antenna side of the splitter it will probably make up for splitter losses.
Ok this is the first time i'v heard of attenuators, maybe it can fix this problem i am having with my spectrum is overloading alot every minute or so it will be fine and then it will go all crazy on me i have tried everything with the gain it doesn't help and i have noticed it is the worst when it's near really strong signals, would a attenuator fix that problem? if so which one or kind should i get? i'll attach two pics showing my spectrum normal and the second showing it going crazy.
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Yeah ur right i'm just gonna go with the rg58 since they seem easier to find and the cheapest.... i'm still on the fence on the tram 1410 discone antenna i have done alot of reading and watched some videos and some people say they suck and the diamond brand or more expensive ones are better which i'm sure it is but is the tram 1410 really that bad? they look almost identical
That strong signal is probably from a paging system transmitter. I have the same trouble and it is really bad. I have three or four towers simultaneously broadcasting on the same frequency from different locations. I have to use a notch filter in my vehicle and two inline at home with my external discone antenna in an effort to reduce/attenuate it.
I purchased them from Dale Parfitt. They cost around $80 each the last time I purchased them. Once you identify the offending frequency, or frequency range, just convey that to him and he can advise on which filter to purchase and he will tune it before sending it to you. If he does not reply right away, just email him again a few days later. He gets busy with commercial orders.
PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts
PAR Electronics Inc. Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave
www.parelectronics.com
Ive had Diamond Discones but not the Tram. I've had many other brands of similar size to the Diamond and have not noticed any difference in performance. I would be surprised if the Tram is noticeably worse than anything else of similar size.
I have that Tram. It works, but I never performed an A/B comparison to the Diamond discone I use 24/7.
I use my Tram as a poor mans portable wide band solution. I store the radials in a PVC tube which is also used as the mast section. A PVC cap on one end and the Tram "head" on the other. What would that be called? ( I store an allen wrench inside the tube as well )
I use my Tram as a poor mans portable wide band solution. I store the radials in a PVC tube which is also used as the mast section. A PVC cap on one end and the Tram "head" on the other. What would that be called? ( I store an allen wrench inside the tube as well )
Hmmm ok .. i do have a FM filter inline but it doesn't help.... i'm not sure if i'm right here but the signals are actually P25 control channels and i think thats what is causing it. where i'm at i can search the entire spectrum from am to 2 ghz and the strongest signals i have are in the 150 to 160mhz range here is a pic of them.
If i had a filter made to block those i wouldn't be able to hear some stuff would i? it's confusing.
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so if you had to buy them again would you go with the tram or the diamond?
it can't be pagers i live nowhere near anyone who would use a pager. if it's the kind of pager i'm thinking of.
paulears
Member
I'd be happy using that one, it follows the usual discone design much more closely. In fairness though your UHF and VHF frequencies are quite close to the 3X rule for a dipole. As in a quarter wave at 150MHz works fine as a ¾ wave at 450. This means 161MHz is close enough to 151 that it's marine band really - 156-162 typically, and my marine 1.4 wave on my van works fine for our UHF business band, our ham repeaters down on 430 and our version of GMRS on 446. You just have maths linked frequencies that make a dipole a decent choice. The discone will do very similar service and is just a bit bigger and heavier.
EDIT-PAGERS
In the UK we have (about half a mile from here) historic paging systems in the 151-154MHz band. They're old, and running quite high power and they swamp stuff either side, plus on the 3rd harmonic, AND it has spurious emissions on all kinds of random frequencies.
paulears
Member
First thing is to think about how university level education teaches you to validate information sources. Any time I read "I have seen" or "I have been told", my filter slams down. A YouTube video from a Phd holding scientist, I trust. A well made video from somebody who may know less than you do, and have experience from watching other YouTube videos? That is VERY different. The thing you are lacking, no offence intended, is some physics and a bit of real experience. If you are worrying about a few feet of flexible cable having an impact, but ignoring where the signal is coming from and getting to those flexible connections, you have taken info in and miss-processed it a bit.
All the popular info on using 75 Ohm satellite designed cable is a good one. So many things to consider with it. It IS very low loss, but it is not a magic bullet. Consider commercial cell phone tower companies, using rigid, large diameter and VERY expensive cable on their towers. The run from the receive antenna to the gear in the radio room might cost them a huge amount of money, and there may be many runs. Do they use RG6? Of course not. Why - it's low loss, and on receive, the impedance mismatch doesn't matter. Actually, it does. In your case, you are going to be throwing signal away in the splitters, that is how they work. In fact, it usually doesn't matter much, because you make it up elsewhere. Antennas with gain, a mast head amp (assuming it is an expensive one that does not create more issues than it solves) all make up the splitter loss. The trouble is that decent splitters also require 50 Ohm loads - that is how they are designed. Your system will have mismatches everywhere - at the mast head, at the splitters, just to save a bit of money. If the cell companies don't do it, neither should you - unless you can live with the unknown performance. for your needs it could be perfect? You seem to have your skills based around the processing of what you collect, not in the basic transmission of low level signals with minimum loss. As I said - maybe it will be good enough. Or will the mismatches and poor antennas produce a lot of issues. The pager thing is not a joke - if you have these big spikes at certain frequencies, performance on the low level ones is compromised. The range between maximum and minimum is fixed. You might need to build or buy notch filters that will have a bandwidth capable of dropping the one you wish to remove, but leaving ones either side unattenuated. These need tuning, and are VERY impedance sensitive. They're also not cheap, even if you have the skills to make them. The science of resonant filters is pretty old now, but not everyone understands them. You also need test gear to align them. SDR receivers have enough gremlins in the works when they have perfect signals to make their performance very variable when you have so many less than ideal items in the chain. You ask us is a certain antenna any good? We look and even without reading the specs (many of which are suspect, I note) we say no, or yes - simply because we've had the experience of flimsy construction, poor electrical design, dubious claims for performance etc etc. What you are doing will almost certainly be rubbish first attempt. You will end up swapping antennas, preamps, feeder cables, adaptors and interconnects. You will add a filter, discard it as useless and try another. If you were a systems engineer, you'd miss a few stage out, but still need adjustments. I fear us feeding you suggestions will not help too much. Trial and error will be much more productive, and you have to plan for it.
My receive installation in the office runs on two antennas on a mast. I transmit from two others. I could have bought RG6 for two of these, but I did not. I think it might even have worked OK for one of the receivers, but one of the transmitters sends periodic data bursts quite close to the receive antennas, and there was a possibility the impedance mismatch might have messed up the filtering. I don't know, I didn't try, I just used the proper cable and it's been trouble free. RG6 might also have been trouble free too? It is the radio version of the guys who tell you how easy it is to run your car on old restaurant discarded oil, but who fill their own car up from the Shell on sale at full price ...............
All the popular info on using 75 Ohm satellite designed cable is a good one. So many things to consider with it. It IS very low loss, but it is not a magic bullet. Consider commercial cell phone tower companies, using rigid, large diameter and VERY expensive cable on their towers. The run from the receive antenna to the gear in the radio room might cost them a huge amount of money, and there may be many runs. Do they use RG6? Of course not. Why - it's low loss, and on receive, the impedance mismatch doesn't matter. Actually, it does. In your case, you are going to be throwing signal away in the splitters, that is how they work. In fact, it usually doesn't matter much, because you make it up elsewhere. Antennas with gain, a mast head amp (assuming it is an expensive one that does not create more issues than it solves) all make up the splitter loss. The trouble is that decent splitters also require 50 Ohm loads - that is how they are designed. Your system will have mismatches everywhere - at the mast head, at the splitters, just to save a bit of money. If the cell companies don't do it, neither should you - unless you can live with the unknown performance. for your needs it could be perfect? You seem to have your skills based around the processing of what you collect, not in the basic transmission of low level signals with minimum loss. As I said - maybe it will be good enough. Or will the mismatches and poor antennas produce a lot of issues. The pager thing is not a joke - if you have these big spikes at certain frequencies, performance on the low level ones is compromised. The range between maximum and minimum is fixed. You might need to build or buy notch filters that will have a bandwidth capable of dropping the one you wish to remove, but leaving ones either side unattenuated. These need tuning, and are VERY impedance sensitive. They're also not cheap, even if you have the skills to make them. The science of resonant filters is pretty old now, but not everyone understands them. You also need test gear to align them. SDR receivers have enough gremlins in the works when they have perfect signals to make their performance very variable when you have so many less than ideal items in the chain. You ask us is a certain antenna any good? We look and even without reading the specs (many of which are suspect, I note) we say no, or yes - simply because we've had the experience of flimsy construction, poor electrical design, dubious claims for performance etc etc. What you are doing will almost certainly be rubbish first attempt. You will end up swapping antennas, preamps, feeder cables, adaptors and interconnects. You will add a filter, discard it as useless and try another. If you were a systems engineer, you'd miss a few stage out, but still need adjustments. I fear us feeding you suggestions will not help too much. Trial and error will be much more productive, and you have to plan for it.
My receive installation in the office runs on two antennas on a mast. I transmit from two others. I could have bought RG6 for two of these, but I did not. I think it might even have worked OK for one of the receivers, but one of the transmitters sends periodic data bursts quite close to the receive antennas, and there was a possibility the impedance mismatch might have messed up the filtering. I don't know, I didn't try, I just used the proper cable and it's been trouble free. RG6 might also have been trouble free too? It is the radio version of the guys who tell you how easy it is to run your car on old restaurant discarded oil, but who fill their own car up from the Shell on sale at full price ...............
Ok thats alot to take in.. i'm no seasoned radio user i am quite new to it all and learning from trial and error i have already paid good money for stuff that turned out to be garbage and nothing like i read on here. That being said how can i use a filter or attenuator to knock down signals that i use i listen to these signals so i don't want to filter them out although some of them i could do with filtering out ya know the encrypted stuff but how exactly do i filter out a specific signal. i emailed that dale guy and explained to him my problem i'm yet to hear back from anyone tho. but the picture i attached below it's those signals that are causing my overload some i could filter out but some i listen to. i know nothing about how a attenuator works i pulled them up on amazon do u think it would be worth purchasing one and trying it if so which one.
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Do they make a filter that is lets say 100mhz to 150mhz ? i was thinking maybe i need to block out more signals and i looked on sdr++ and their is alot of signals that are just useless it's nothing on them it's from other stuff i guess but can i get a filter that would maybe block out those? all i can find are FM filters and AM filters.
Filters in that range show up on eBay cheap.
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