Power Rating of 90 degree N adaptor

[VK2DVZ]

Hi all,

I have use for a 90 degree M/F N-type adapter. I found a 'new' one sealed inside a plastic bag amongst my collection and is labeled 91836 UG-27D/U. It appears to be silver plated with gold pins.

I am wondering what power rating it may handle on 144MHz as it will be placed on equipment within about 400mm from the output of my 2m valve PA with 500-600 watts being fed through it, for EME or MS purposes.

I will have to use a M/M N-type adapter also, attached to the F side of the adapter in question, to compete the equipment connection. I hope it too will be happy at the required power level also. I am trying to avoid using more short lengths of patch leads to minimise losses,etc.

Any one have ratings for such connectors or can point me to relevant data sheets?

Regards,
Ross VK2DVZ

[VK2XSO]

Ah ! I love a good thought question like this.

Ok, there are some standards for N type connectors. Starting with the breakdown voltage for N type connectors of 1500V. The actual breakdown is much higher than this, about 2500V, but the safe rating is obviously lower.

There is also a maximum insertion loss which is about 0.1dB. But this too is the absolute maximum and the actual insertion loss is much less.

At 600W the voltage is about 1800V so you're pushing it into the limits of the connector.
With the 0.1dB insertion loss you will probably heat up the connectors with something around 5 to 10W. You'll be lucky to warm it up

I would think that the N connectors in the system will hold out ok.

If you were really worried, then I would just take it to the next level and use DIN connectors. They are as common as dirt on the surplus market because hams have no idea how to use them. It's not uncommon to see five metre lengths of heliax with a male DIN on one end an a female N on the other.
They are ten times better than N type connectors in every way except physical size. They're big connectors.

Assuming you run LDF5-50 up the tower, an SCF12-50 tail from the amp to the heliax with male DIN's on each end and a female DIN on the heliax.
At the top of the tower another Female DIN with a Male DIN one end of RFS SCF12-50 with a male N type for the connection to the yagi.

Sounds expensive, but the cost of this stuff on the surplus market (not the long run of LDF5-50) would be less than running and terminating tails in RG213 with N connectors. Yick ! Why would anybody do that

[VK4OX]

[quote="VK2XSO"]

"At 600W the voltage is about 1800V so you're pushing it into the limits of the connector.
With the 0.1dB insertion loss you will probably heat up the connectors with something around 5 to 10W. You'll be lucky to warm it up"


Assuming 1500Vrms is the safe limit for N connectors, and assuming a 1:1 VSWR throughout a 50 Ohm system, then the power limit is 1500^2/50 = 45000 Watts rms, so voltage breakdown is not a factor in amateur systems. At 1000W pep, the peak voltage is 224V .

Insersion loss is the main problem. As the frequency goes up, so do the losses. A 0.1 dB loss in a 1000W system is 23 Watts. Any connector dissipating 23 Watts will get HOT.

I have had no trouble with M-F 90 deg N connectors up to 400W pep at 1296MHz. I HAVE had trouble with SOME, (Chinese), M-M 90deg connectors. One got so hot at 1296MHz it fell apart and exposed the manufacturer's method of making the right angle bend on the centre conducor. They had used a beryllium -copper SPIRAL spring to negotiate the bend!! This connector was totally useless at anything above 30MHz!!

To test your system, run a few periods of fsk441 and then feel the temperature of each adaptor in your system.. Assuming they are far enough away from your pa to discount heat conduction from the pa itself, the touch test will expose suspect adaptors.

7/16 DIN connectors are very good, but finding an antenna change over relay in DIN architecture, is not so (cheap) easy.

73, Adrian. VK4OX.

[VK3AUU]

I think someone has slipped a decimal point in the voltage calculation above.
In a past life I have found that the current flow through the connector pin is the main problem. If the pin and its mating socket are gold plated it will be OK.

David

[VK2DVZ]

Thank you to those who responded to my inquiry, both here and privately.

I 'smoke tested' the adapter in question with several sequences of jt65b with about 500 watts passing through it and all was OK and the temperature remained unchanged.I will leave it in circuit.

During an extended session on the moon I will perform further checks for any indication of temperature rise.

[VK2KRR]

Ross, if u had one available, one of those infrared thermometers would be handy. Point it at the component in question.

[VK2XSO]

High quality right angle N connectors are also plentiful on the surplus market.
If you're going to Wyong, find me and I'll give you a couple.
And some DIN connectors if you want to play with them