Would someone please explain to me why TNC connectors are so expensive. I just had my 430 upgraded to WAAS and now need a TNC connector for the antenna. I checked with several sources and these connectors are averaging around $26.00 and up each. I searched on Ebay and saw an auction for a bag of 100 TNC connectors for RG 58/RG400 with delrin and gold plated center pin, crimp type for $25.00 plus shipping. I really don't need a 100 of these but, this is a far better deal than buying one connector for the same price. What is the difference???
Van's Air Force
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TNC connectors
- Thread starter pa24
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az_gila
Well Known Member
Old cable...
Jamie... that might not be a good solution for the G-430/530 Upgrade to WAAS case.
This FAQ from Penn Avionics states why... If you are going to use the G-430 for IFR use, the manufacturer's requirements should be met....
The existing cable is probably not up to specification for the upgrade unit...
Why does the exiting GPS antenna coax need to be inspected / replaced?
(Garmin manual 190-00357-02 section 3.10.1) The original Garmin 400/500 installation manual simply stated that the GPS antenna coax had to be 50 ohm coax and could not be have more than 10db of signal loss at 1500 mhz. This was an easy spec to meet with almost any coax configuration, and many installations were performed using RG58 coax that has a single shield. The new 400/500 WAAS equipment is very sensitive to the exact amount attenuation between the GPS antenna and the panel mount 400/500 receiver, and the type of shielding on the coax. The new 400/500 WAAS install manual states that the GPS antenna coax cable loss, including connectors, shall be between 3db and 7db at 1500 MHz in order to maintain proper rejection to interference signals. Also the coax must have two shields (i.e. RG-58 coax is not acceptable). If the measured loss is greater than 7db, the coax will need to be replaced with low loss coax to bring the attenuation down. If the measured loss is less then 3db, extra coax or an external attenuator will need to be installed to bring the attenuation up to 3 db. Penn Avionics has purchased advanced coax test equipment to measure this db loss at 1500 MHz. If the existing GPS coax meets the 3db - 7db spec and the shielding spec, then no changes should be necessary. If the existing GPS coax loss falls outside of this specification, or is of the RG58 type, the coax will require rework / replacement to comply with the new WAAS guidelines. Penn Estimates that to replace the GPS coax will run approximately $150 - $395 depending on the aircraft and the location of the GPS antenna. Larger aircraft with aft mounted GPS antennas will require the interior to be opened up to gain access to the GPS coax. This may result in additional labor charges
http://www.pennavionics.com/WAAS_UPGRADE.html
Straight RG-400 can be used without measurement, but the length is critical...
4. Yes it comes back with a new antenna, but not coax. Your avionics shop may provide it, but Garmin does not. The new antenna now requires a TNC fitting opposed to the BNC on the original antenna. Now here is something most do not know. Garmin requires the new coax to be RG-400 and there is a specific length. It can't be less that 13ft long or greater than 35ft. At our shop if we are doing an update on a certified plane there is no question, we must follow these requirements.
...this is from an Avionics shop in a previous VAF posting... post #4
http://www.vansairforce.com/community/showthread.php?t=16853
gil A
Jamie... that might not be a good solution for the G-430/530 Upgrade to WAAS case.
This FAQ from Penn Avionics states why... If you are going to use the G-430 for IFR use, the manufacturer's requirements should be met....
The existing cable is probably not up to specification for the upgrade unit...
Why does the exiting GPS antenna coax need to be inspected / replaced?
(Garmin manual 190-00357-02 section 3.10.1) The original Garmin 400/500 installation manual simply stated that the GPS antenna coax had to be 50 ohm coax and could not be have more than 10db of signal loss at 1500 mhz. This was an easy spec to meet with almost any coax configuration, and many installations were performed using RG58 coax that has a single shield. The new 400/500 WAAS equipment is very sensitive to the exact amount attenuation between the GPS antenna and the panel mount 400/500 receiver, and the type of shielding on the coax. The new 400/500 WAAS install manual states that the GPS antenna coax cable loss, including connectors, shall be between 3db and 7db at 1500 MHz in order to maintain proper rejection to interference signals. Also the coax must have two shields (i.e. RG-58 coax is not acceptable). If the measured loss is greater than 7db, the coax will need to be replaced with low loss coax to bring the attenuation down. If the measured loss is less then 3db, extra coax or an external attenuator will need to be installed to bring the attenuation up to 3 db. Penn Avionics has purchased advanced coax test equipment to measure this db loss at 1500 MHz. If the existing GPS coax meets the 3db - 7db spec and the shielding spec, then no changes should be necessary. If the existing GPS coax loss falls outside of this specification, or is of the RG58 type, the coax will require rework / replacement to comply with the new WAAS guidelines. Penn Estimates that to replace the GPS coax will run approximately $150 - $395 depending on the aircraft and the location of the GPS antenna. Larger aircraft with aft mounted GPS antennas will require the interior to be opened up to gain access to the GPS coax. This may result in additional labor charges
http://www.pennavionics.com/WAAS_UPGRADE.html
Straight RG-400 can be used without measurement, but the length is critical...
4. Yes it comes back with a new antenna, but not coax. Your avionics shop may provide it, but Garmin does not. The new antenna now requires a TNC fitting opposed to the BNC on the original antenna. Now here is something most do not know. Garmin requires the new coax to be RG-400 and there is a specific length. It can't be less that 13ft long or greater than 35ft. At our shop if we are doing an update on a certified plane there is no question, we must follow these requirements.
...this is from an Avionics shop in a previous VAF posting... post #4
http://www.vansairforce.com/community/showthread.php?t=16853
gil A
They are expensive because they can get away with it. Go to the Newark web site. It may take some poking around but you can find them at this link for 3-8 bucks. Make sure your not getting reversed polarity and the ohm rating is what you need for your application
http://www.newark.com/jsp/search/br...001&Ntt=TNC+connectors&Ntx=&_requestid=240149
Go to the Newark web site. It may take some poking around but you can find them at this link for 3-8 bucks. Make sure your not getting reversed polarity and the ohm rating is what you need for your applicationhttp://www.newark.com/jsp/search/br...001&Ntt=TNC+connectors&Ntx=&_requestid=240149
frankh
Well Known Member
Good deal
How long is the adaptor from Frys?
I have my antenna on the glaresheild (hoping it will work there) and so I am limited how far down the connector will poke.
Frank
How long is the adaptor from Frys?
I have my antenna on the glaresheild (hoping it will work there) and so I am limited how far down the connector will poke.
Frank
The good TNC connectors are expensive because they are usable to 18 GHz (possibly further). This is 12-15x GPS frequencies. What you'll find is that they are better made than the cheapies. Also, the cheap connectors tend to oxidize more quickly (thinner plating, etc.). They also make less of them since the king in the microwave world is the SMA.
What you also may not know is that TNC connectors (as any threaded MIL connector) have a torque spec. For the "good" stainless steel connectors, it is 12-15 in-lbs. For the cheapies, if they are made of brass, it is about 4.1-6.1 in-lbs. If you have a datasheet from the manufacturer, make sure to consult it.
What you also may not know is that TNC connectors (as any threaded MIL connector) have a torque spec. For the "good" stainless steel connectors, it is 12-15 in-lbs. For the cheapies, if they are made of brass, it is about 4.1-6.1 in-lbs. If you have a datasheet from the manufacturer, make sure to consult it.
Jamie
Well Known Member
The adapter is pretty small. Here's a picture of mine (this is an old picture when my plane was still in the garage, so the FWF stuff isn't done yet):
Fry's also sells the solder and crimp type TNC connectors. I can't say anything about their quality. I don't have a WAAS GPS, but my GPS install works great.
I'm not sure what you mean, Gil. The instructions don't forbid the use of any adapters, only that the minimum db loss be met. Since it must be installed per the manufacturer's recommendations, I guess all of these people who are installing these 430Ws are also installing the antennas on an external surface of the aircraft too, right?
az_gila
Well Known Member
TSO requirements
Jamie... the other issue that occurs with the WAAS upgrade has to do with the quality of the shielding of existing cable. If you did not use RG-400 for the original installation, the cable needs to be replaced anyway, and the RG-400 has the min. and max. specifications.
If you don't have an external surface antenna, you are probably not meeting the installation requirements to keep your systems TSO. You might have some extra attenuation that could compensate for a shorter co-ax length.... but without a true RF measurement, you don't know... and yes, I would say the TSO is not valid...
I don't have a copy of the 430 WAAS Installation Manual, so I can't say if the adapter is legal... you can check the wording to see what it says are the specific cable requirements.
Your choice whether that bothers you or not...
gil A
The adapter is pretty small. Here's a picture of mine (this is an old picture when my plane was still in the garage, so the FWF stuff isn't done yet):
....
Fry's also sells the solder and crimp type TNC connectors. I can't say anything about their quality. I don't have a WAAS GPS, but my GPS install works great.
I'm not sure what you mean, Gil. The instructions don't forbid the use of any adapters, only that the minimum db loss be met. Since it must be installed per the manufacturer's recommendations, I guess all of these people who are installing these 430Ws are also installing the antennas on an external surface of the aircraft too, right?
Jamie... the other issue that occurs with the WAAS upgrade has to do with the quality of the shielding of existing cable. If you did not use RG-400 for the original installation, the cable needs to be replaced anyway, and the RG-400 has the min. and max. specifications.
If you don't have an external surface antenna, you are probably not meeting the installation requirements to keep your systems TSO. You might have some extra attenuation that could compensate for a shorter co-ax length.... but without a true RF measurement, you don't know... and yes, I would say the TSO is not valid...
I don't have a copy of the 430 WAAS Installation Manual, so I can't say if the adapter is legal... you can check the wording to see what it says are the specific cable requirements.
Your choice whether that bothers you or not...
gil A
atreff
Well Known Member
From Tony at Stark
I have a 12inch run to my WAAS antenna, will be installing the TNC connector when I get it from Stein, therefore I have not received a satellite lock yet, no antenna yet.
In the meantime, I pinged Stark Avionics on the 13' antenna run requirement for my new 430W. I told him we were disucssing the TNC connectors and RG-400 run length on our RV Forum. Tony had this to say:
"According to the latest 400W and 500W series installation manuals, there must be 1.5 to 6.5 db of signal loss between the antenna and GPS receiver. The last revision to the manuals called out for between 3.5 and 7 db. So, the message you are reading on the forum must be an older message. With the latest db requirement, you can get away with around 6 to 7 feet of RG-400 to attain 1.5 db of signal loss. If you have a 12 inch piece of coax in there now, YOU NEED TO CHANGE IT OUT. You?ll just have to coil up a bunch of extra coax. There is no way around this."
Thanks to all for the head's up. I would have stayed with my 12" coax run and crimped on my very expensive 90 degree TNC connector, only to have to buy another one!
Art in Asheville
I have a 12inch run to my WAAS antenna, will be installing the TNC connector when I get it from Stein, therefore I have not received a satellite lock yet, no antenna yet.
In the meantime, I pinged Stark Avionics on the 13' antenna run requirement for my new 430W. I told him we were disucssing the TNC connectors and RG-400 run length on our RV Forum. Tony had this to say:
"According to the latest 400W and 500W series installation manuals, there must be 1.5 to 6.5 db of signal loss between the antenna and GPS receiver. The last revision to the manuals called out for between 3.5 and 7 db. So, the message you are reading on the forum must be an older message. With the latest db requirement, you can get away with around 6 to 7 feet of RG-400 to attain 1.5 db of signal loss. If you have a 12 inch piece of coax in there now, YOU NEED TO CHANGE IT OUT. You?ll just have to coil up a bunch of extra coax. There is no way around this."
Thanks to all for the head's up. I would have stayed with my 12" coax run and crimped on my very expensive 90 degree TNC connector, only to have to buy another one!
Art in Asheville
Appreciate all those who have responded. I guess I'll just have to bite the bullet and spend the 25 plus bucks on one connector. I mounted my antenna forward of the firewall and used a 2 1/2 foot length of RG 400. I have yet to turn my 430w system on. I have another stupid question - how do you measure the db signal loss between antenna and receiver? If necessary, I'll run another coax and coil it according to Tony's answer but, I want to make sure I have the proper signal loss before wasting all this money.
Thanks,
Roy
RV 7 Finishing
Thanks,
Roy
RV 7 Finishing
Definitely not a stupid question, but I sure can't give you a smart answer. At work, we use an outrageously expensive piece of equipment called a "network analyzer" (our particular model costs over $150,000). A cheaper solution is a signal source and a power meter, but that's still way more than anyone here would spend. Without asking around, I would venture a guess that a good avionics shop would have enough stuff to kludge this measurement.
I can think of a way to do it if the GPS has a built in signal strength meter, but it would involve needing the GPS on a bench in clear sky view. Since I don't know if the minimum loss spec on the cable is related to damage levels (I doubt it, but I'm not going to risk someone else's GPS) I'm not going to post the procedure that's in my head right now without trying it first.
Cheapest solution is to look at the loss spec for the particular coax cable you have and hope they measured it right. These are usually given as dB / ft or dB / 100 ft. Adaptors and connectors will add probably no more than a couple of tenths of a dB to the cable's loss.
Yea, that would certainly be useful information if I had the installation manual. You are saying that you received an installation manual with your 430? Unfortunately, my unit came with pilot's reference and operating manuals only, and it's a brand new unit.
atreff
Well Known Member
430 manuals
Garmin no longer publishes install manuals on paper, soft copies (.pdf) are all available thru your dealer, I had to ask for mine.
Send me an email and I'll send you a zip file with the 430 manual in it. It' 8MB, so I have to compress it. 220+ pages.
Art in Asheville
[email protected]
Garmin no longer publishes install manuals on paper, soft copies (.pdf) are all available thru your dealer, I had to ask for mine.
Send me an email and I'll send you a zip file with the 430 manual in it. It' 8MB, so I have to compress it. 220+ pages.
Art in Asheville
[email protected]
Gsuit
Well Known Member
Straight from the installation manual:
NOTE
If the existing coaxial cable is terminated with a BNC connector and the GPS WAAS antenna being installed has a TNC connector, a TNC-to-BNC adapter such as P/N 1-1478013-0 from AMP (Tyco) may be used. The adapter will add 0.5 dB to the overall GPS antenna cable loss.
"Penn Estimates that to replace the GPS coax will run approximately $150 - $395 depending on the aircraft and the location of the GPS antenna."
Andrew's FSJ1-50 is available for $1.29/ft, and BNC connectors are $11. Its loss is half of that of RG58, and will easily meet the loss spec. See the posting I made earlier about its use and the loss comparisons made by Mike Cherney which he posted on the canard site. By the way, the "N" and "C" in these connectors are the initials of the last names of the two guys with Bell Labs who invented these connectors around WWII. The "B" stands for bayonet, and the "T" stands for threaded.
Andrew's FSJ1-50 is available for $1.29/ft, and BNC connectors are $11. Its loss is half of that of RG58, and will easily meet the loss spec. See the posting I made earlier about its use and the loss comparisons made by Mike Cherney which he posted on the canard site. By the way, the "N" and "C" in these connectors are the initials of the last names of the two guys with Bell Labs who invented these connectors around WWII. The "B" stands for bayonet, and the "T" stands for threaded.
