Antenna for BCD436HP
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iMONITOR
Silent Key
Diamond SRH77CA is the same, but terminates to an SMA connector, which is what your BCD436HP uses.
https://www.universal-radio.com/catalog/scanants/2368.html
https://www.universal-radio.com/catalog/scanants/2368.html
iMONITOR
Silent Key
I really wish they'd all stick to BNC connectors. Even my tiny BCD325P2 has a BNC, much stronger.
jonwienke
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Wrong on both counts.
There are 50Ω and 75Ω BNC connectors. The adapter supplied with the 436 is a 50Ω adapter, so no impedance mismatch.
The base of the BNC adapter is approximately twice the diameter of the base of SMA antennas. So when a sideways force is applied to a BNC antenna, the tension that force induces on the SMA connector is approximately half of what would be applied to the SMA connector with a SMA antenna.
Ubbe
Member
Jon, you missunderstood cmdrill. He was refering to that putting a sma-BNC adapter on the scanners sma connector would strain the scanners connector. And putting an adapter between scanner and antenna would cause a change of the groundplane, almost like using a 1/4 wave antenna directly connected to a coax without using any groundplane radials, and would probably give both a frequency and impedance mismatch with that 2 centimeter raise of the antenna from the groundplane. A 10% change of the antenna lenght is a 10% change in frequency. Thats something like a tuned 800MHz antenna being lowered to 700MHz.
/Ubbe
/Ubbe
jonwienke
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That makes even less sense. Tightening the adapter puts the same strain on the sma connector as tightening an antenna. And the wider base of the adapter means less leverage straining against the connector when a bending force is applied to the antenna.
And the adapter will have far less effect on the ground plane than how the user holds the radio. Especially considering that the outer surface of the adapter is RF ground.
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Fast1eddie
Member
All valid points, but I really would not concern myself with any perceived impedance mismatch....First, without access and proficient use (and understanding the interpreted results) of sophisticated RF impedance measuring equipment, to me that is a meaningless concern. The 436's sensitivity is smoking hot and any measurable difference is more than made up by the receiver's sensitivity. I concern myself with the antenna quality (No cheap Chinese junk, go with a quality commercial product) and feedline if used as portable - mobile. I've witnessed well intended monitors attempting to monitor VHF signals with a UHF stubby made for 450 Mhz confused as to why they are not hearing anything, if anything at all. Surplus ham dual band HT antennas from the older school Yaesu radios and Standard are excellent! You'll want to look for Yaesu FT 727 and Standard 528 and above, look for a wide barrel base. Likewise on low band....Cheap coax with multiple splices (yes, splices with duct tape!), not inline barrel connectors....Poorly installed BNC and or PL-259's....Was a radio tech for years and I have seen it all....Then I became a cop and my eyes were truly opened, but that's another story.....But I digress....
I purchased a quality flange SMA to BNC adapter, cost was $14.00 from Uniden, however the machining is perfect (poor threading also leads to signal loss, stay away from cheap connectors...Always go top shelf if you seek positive results, as is anything in life, especially footwear! and the base is wide enough to offer sufficient support to a larger portable antenna.
Now I use several different antennas depending on my monitoring environment. Favorites are the Diamond SRH77CA and the BNC equivalent, same antenna but I typically leave the adapter in place....The Condor Tuned Duck is great, but admittedly looks like bedroom toy, so expect lewd comments, however the ladies will coyly smile....When I monitor Airband, I have duck made for civilian and military aero bands. Bought it (and everything else from Universal Radio, great folks to deal with, love their kats), and if I take it into town and want to monitor strictly UHF, I go with a stubby duck I appropriated from one of our department's junk portables that had seen better days.
Going mobile portable, I have again several mobile antennas....Nothing beats the older Antenna Specialists tri band monitor whips, excellent for low band but you will stress the roof mount and hit low lying tree branches if you have a high profile vehicle, such as my Escape. I did use a Austin tri band mobile which could also be used to transmit on several ham bands, but the internal copper tab which contacted with the NMO mount broke and am working on a fix. I now use a shorty tri band I picked up from Scanner Master, and works extremely well out of band, especially for air band. I've always used top shelf coax and go with 3/4 hole mount. Mag mounts work, but consider them for temporary use, likewise with glass mounts. Drill the hole and use solder connectors! No crimp! You want a solid RF connection. Anything less will lead to problems in a everchanging mobile environment. Also scrape away the paint where the mount secures to the roof, remember you want a high integrity vehicle ground which is crucial if one likes to monitor low band DX. Like the 70's, I seek a return to low band...it's a blast when the band is open.
Getting back to the SMA - BNC adapter, I never torque the thing down. Snug it and when the plastic washer becomes flatter than a mess hall pancake (my sincere apologies to any past or present mess NCO's, I appreciate your chow and got fat off it) replace it. Any hardware store will carry them, or you can make one out of somewhat thick cardboard. Push down on the BNC portion of the antenna and gently twist when removal time comes....And never carry it by the whip as my now ex wife did.
Good DX and 73,
ed
I purchased a quality flange SMA to BNC adapter, cost was $14.00 from Uniden, however the machining is perfect (poor threading also leads to signal loss, stay away from cheap connectors...Always go top shelf if you seek positive results, as is anything in life, especially footwear! and the base is wide enough to offer sufficient support to a larger portable antenna.
Now I use several different antennas depending on my monitoring environment. Favorites are the Diamond SRH77CA and the BNC equivalent, same antenna but I typically leave the adapter in place....The Condor Tuned Duck is great, but admittedly looks like bedroom toy, so expect lewd comments, however the ladies will coyly smile....When I monitor Airband, I have duck made for civilian and military aero bands. Bought it (and everything else from Universal Radio, great folks to deal with, love their kats), and if I take it into town and want to monitor strictly UHF, I go with a stubby duck I appropriated from one of our department's junk portables that had seen better days.
Going mobile portable, I have again several mobile antennas....Nothing beats the older Antenna Specialists tri band monitor whips, excellent for low band but you will stress the roof mount and hit low lying tree branches if you have a high profile vehicle, such as my Escape. I did use a Austin tri band mobile which could also be used to transmit on several ham bands, but the internal copper tab which contacted with the NMO mount broke and am working on a fix. I now use a shorty tri band I picked up from Scanner Master, and works extremely well out of band, especially for air band. I've always used top shelf coax and go with 3/4 hole mount. Mag mounts work, but consider them for temporary use, likewise with glass mounts. Drill the hole and use solder connectors! No crimp! You want a solid RF connection. Anything less will lead to problems in a everchanging mobile environment. Also scrape away the paint where the mount secures to the roof, remember you want a high integrity vehicle ground which is crucial if one likes to monitor low band DX. Like the 70's, I seek a return to low band...it's a blast when the band is open.
Getting back to the SMA - BNC adapter, I never torque the thing down. Snug it and when the plastic washer becomes flatter than a mess hall pancake (my sincere apologies to any past or present mess NCO's, I appreciate your chow and got fat off it) replace it. Any hardware store will carry them, or you can make one out of somewhat thick cardboard. Push down on the BNC portion of the antenna and gently twist when removal time comes....And never carry it by the whip as my now ex wife did.
Good DX and 73,
ed
jonwienke
More Info Coming Soon!
I'm right, for the same reason 2" diameter pipe takes more force to bend than a 1" diameter pipe with the same mass per linear inch. It's a fairly simple stress analysis.
Yep. Jon's right. If he were not, every antenna would have to be put directly on the antenna connector of a radio and COAX would not exist. It, too, merely extends the feedpoint, and if everything is 50 ohm, there is no mismatch. The same is true for the adapter. Think of it as a 1/2" feedline.
The base of the adapter rests on the scanner and provides support that does not exist when using an SMA antenna. With SMA, all the strain is on the connector. With the adapter, most of the strain is on the case of the scanner and very little is on the connector. That is IF you use the OEM adapter. There are adapters that are, well, let's call them POS (you figure out the acronym). They offer no support and are worse than the SMA alone. But, if we are talking all OEM parts, the adapter is much better.
All other issues aside, I too was not happy about the SMA connector on the 436 when it first came out. But I have learned it's not all that bad. Before when a BNC went bad, I had to open up the scanner to replace it. Now, I just replace the adapter which is a much faster and easier process. My SMA should last basically forever.
So, my vote is for BNC. This also makes changing antenna much faster and safer while in a car (it also can be a one-handed process).
The base of the adapter rests on the scanner and provides support that does not exist when using an SMA antenna. With SMA, all the strain is on the connector. With the adapter, most of the strain is on the case of the scanner and very little is on the connector. That is IF you use the OEM adapter. There are adapters that are, well, let's call them POS (you figure out the acronym). They offer no support and are worse than the SMA alone. But, if we are talking all OEM parts, the adapter is much better.
All other issues aside, I too was not happy about the SMA connector on the 436 when it first came out. But I have learned it's not all that bad. Before when a BNC went bad, I had to open up the scanner to replace it. Now, I just replace the adapter which is a much faster and easier process. My SMA should last basically forever.
So, my vote is for BNC. This also makes changing antenna much faster and safer while in a car (it also can be a one-handed process).
If your wanting a good quality antenna, Get a D130j discone roof top Antenna about 20ft above my roof with LMR 400 cable. That is what I run on my 536hp 436hp and my psr 500 and my CB. I monitor hundreds of miles of agencies.
Ha! I don’t wear my radios on my belt. I have my 436 and PSR 500 in my house with that cable and antenna setup and I have my 536hp in my truck with that same cable but using a NMO roof top antenna and a 70inch metal whip. Works Amazingly Well.
Understood. But most people buy portable scanners to be used portable, not for base or even mobile use. A Discone is not exactly a good portable antenna.
...(or mobile for that matter)
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