tweiss3
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Posts posted by tweiss3
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1 hour ago, dosw said:
While the choice of CTCSS tones is not entirely random, it may as well be. There are common conventions, like avoiding adjacent tones in a given overlapping area, avoiding tones that are harmonics of power lines, that sort of thing. I think in some cases it's more about "legacy conventional wisdom" than about "real world issues in 2025." But as far as repeaters following a pattern, what you might be seeing is either a freak coincidence, or regional conventions that may have some historical rationale. Not any broadly adopted pattern.
Actually, your local repeater coordination body (typically won't answer anything and are useless), have recommended tones (2-5 of them) for each region of the area which they coordinate. These are Ohio's recommendations, not requirements, but it keeps adjacent pairs from using the same tones.
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Talk around is a great function commonly used in commercial radios. It switches your TX frequency to the output of the repeater to operate in simplex. I personally think it should be used more, but it's only as good as those trained how/when to use it.
- H8SPVMT and AdmiralCochrane
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I have used a RigExpert Stick XPro clamped in a tripod that gave a good repeatable picture of the overall bandwidth of some commercial antennas. I was able to see how "bad" the Harris UHF antenna was compared to the AllBand antenna on VHF was. For the other basic designs, i.e. 1/4 wave, 1/2 wave, etc., those have know performance from physics and aren't worth even sweeping.
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10 minutes ago, GreggInFL said:
This appears to be a fiberglass tube. So, I should be able to tune it to 462 by shortening it roughly 7", right?
A little less to split 462 and 467?
(<PE but not an EE)
No. It's probably a colinear array. Unless you want to redesign the whole array, it's not worth touching. If you are less than 3:1 at 462, leave it alone.
- SteveShannon, GreggInFL and LilRedDog
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Interesting concept. Not exactly sure how it's accomplished with a single duplexer though, unless both sides (462&467) are full RXTX units. Either way, talk about long squelch tails and lag.
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Ok, so not all encryption is compatible between manufacturers. I'll give a common example.
Both Kenwood and Motorola had DMR radios, but their "basic" privacy is not compatible between the two. Motorola's is a 16bit XOR, Kenwood's is a bit different, thus incompatible. The "basic" privacy is typically a non-standardized encryption that is for basic privacy at little/no cost. Now, you can use Enhanced Privacy/Enhanced Encryption in Moto/Kenwood DMR, because they use a standard, ARC4/RC4 40bit encryption. Same goes for other standard methods of encryption such as DES (64bit) and AES256 (256bit) which is compatible between manufacturers, as secure interoperability is required. These methods of encryption can be used with NXDN and P25, based on options available (both cost and free) for each radio.
Loading encryption, when meeting opsec/FIPS requirements, creates the key, which is stored in either a hardware or software vault, and then loaded into the radio via manufacturer specific software, or with a hardware device called a keyloader. The keys can be transferred between secure devices (keyloaders/vaults) but after creating and storing them, you can never view what the key is again, so store it properly.
In the case of many of these Chinese radios, security and standards are typically not followed. You basically copy the key into the software, apply it to the digital channel desired and that's it. Keep in mind, since they don't follow the standards, the encryption may not be compatible with others. The AES could be AES128, or just a completely made up 256 encryption method applied to DMR different than the standard, thus not compatible with other radios using industry standards.
@WRYZ926SINCGARS uses frequency hopping for security, which not only doesn't show up on a scanner/close call, it's impossible to follow without the starting frequency and hop-set, which is why it's just as secure as AES, if not more.
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Interesting results, pretty maxed out for a "mobile" duplexer.
As for your coverage, I have to wonder if your antenna is mismatched for priority coverage. It's not uncommon to go for higher gain, then shooting your RF pattern over your intended close coverage. This isn't an uncommon problem. No doubts that neighbor's household items and the vegetation can be part of the issue, but unless its all pine, I have my doubts that it is the next biggest issue you have to correct/improve.
- marcspaz and SteveShannon
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I have a handful of them for various uses/projects. Other than being rated for 5W, they do great, just spend some time and align it correctly, they can get sensitivity down to about -120db or better.
The FCC approval occurred before Part 95E approvals were a thing, previously they just called it Part 95, so yes, its approved. Now, your amplifier won't be approved.
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I would also be weary of adjusting the power using the input voltage. That sounds dangerous for the long term survival of the circuits. That typically isn't the correct way to adjust a transmitter.
- marcspaz and SteveShannon
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If you look at the table, it's performance narrows and insertion loss increases as you approach 5MHz spacing. There is no way in hell that will have acceptable performance at 3MHz spacing.
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2 hours ago, WRDJ205 said:
Google is sending me to the same link as i found earlier ...
Repeater Duplexer 50W UHF 6 Cavity Duplexer SGQ-450D -
Be careful, that specification indicates a minimum spacing of 8-10MHz between RX and TX, but the US standard for UHF is 5MHz.
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Or hoarded by Crown Castle or another monopoly.
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2 hours ago, marcspaz said:
I wouldn't put a mobile duplexer in orbit. That would be a disaster waiting to happen.
I agree, but I don't see another way to remain within GMRS, unless you use two antennas and mount them like a dipole and only use 1/2W.
I have a trunked P25 P1 "site" in my living room where the CC is 0.05MHz below the VC, RX antennas are pointed up, and TX antennas are left and right away from each other. Works well, but it's only putting out 0.1W.
In theory, its a $7+M idea that would likely just become space junk before it is used.
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22 minutes ago, marcspaz said:
There are no restrictions on putting a GMRS satellite in orbit. We should start a crowd-funded account to make that happen.
While correct, I suspect the crowd-funding would be significantly short of the cost to get one up in near earth orbit. I wonder what space dust and the extreme temperatures would do to a "mobile" duplexer though.
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As others have said, ham UHF vs GMRS, you won't notice a difference with HTs. VHF high (2m) will get a bit further under normal conditions. VHF low (6m, 50MHz) gets to the point that an adequate antenna is the issue for HTs. It will act the same as 2m without atmospheric propagation helping, but when propagation is open, there are thousands of stories of talking across the USA on only 5w.
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I need to get back to studying for AE. Same as last years study course, life got busy and I'm behind again.
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Heh. My wife doesn't necessarily participate, but finds them useful at times. She didn't really say anything after she saw my last purchase order other than "that's a lot of money" then walked away and didn't mention it again.
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As mentioned, testing of an HT antenna is nearly impossible to get completely accurate results. It should also be noted that sometimes a "better" antenna will cause the radio to perform worse due to RF saturation. That being said, for the APX, the Motorola antenna will work the best for that radio.
- SteveShannon and WRUU653
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Other than shortcuts, the keyboard is only useful for DTMF tones, which could be used to control a repeater's features, such as changing the input tone, or disabling the repeater during a malfunction. It's not a huge selling point for many radios.
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Yea, I had 2 XPR3500 that had bad antenna sockets. Was fixed in about 20 minutes with the soldering station.
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It's in the rules.
Fixed station. A station at a fixed location that directly communicates with other fixed stations only.
Base station. A station at a fixed location that communicates directly with mobile stations and other base stations.
47 CFR 95.303
An example of a fixed station would be an RF link between 2 repeaters. They only talk with each other, at fixed locations.
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I'm a fan of distance contacts on 80m while doing 70 down the highway. I don't really ever have time to sit longer than 15 minutes.
Repeater Off-Sets are different with HAM.
in Amateur Radio (Ham)
Posted
Well, SouthEast Repeater Association (the TN coordination body) has recommended tones.
100.0 is the common, and if you are on the edge of TN middle and TN east, what you notice is on purpose......