Well, the embassies that I saw were all in an urban area at the shores
of the Med. There was no room for big antenna arrays. The HF antennas
had to fit completely on the embassy rooftops, hence most were fairly
short dipoles.
Regarding the B&W broadband dipole, I don't know why so many amateur
emergency groups buy them for EOC's. You only need a broadband antenna
if you're doing frequency hopping or using unskilled operators who can't
use an antenna tuner. Autotuners take care of the skills issues, and
most amateur radio emergency comms takes place on only a couple of
bands, and usually on spot frequencies. There is a real penalty with a
resistively loaded antenna like that: Its only about 12% efficient on 75
meters.
Hey, remember the Teletron Slinky Dipole from the late 60's and early
70's. Their ads claimed that they were used by the army and state
department. Maybe they were part of the evacuation kit, of a backup
antenna for the attic. I built a Slinky Dipole for my attic. Two
slinkys, and a 1:1 Radioworks balun. It is resonant at about 7.5 MHz.
With a tuner, it will load on 80 meters, but it is about 12-15 deb down
from my outside 80 m dipole.
73,
Bob WB2VUF
Dave Heil wrote:
> Ken Brown wrote:
>>> Only in very few outlying Embassies are there any over the air type
>>> communications. Everything is or was on line encrypted. Basically any
>>> outside wiring or antennas not allowed.
>>>
>>>
>>>
>> I have seen log periodics on buildings in Europe. I notice those kinds
>> of things. Most times, when I have investigated to see what is in the
>> building on which the antenna is mounted, it has been a foreign embassy.
>
> Some countries *used*, at least until 2000, quite a bit of HF. The
> Chinese are an example. The Bulgarians used to have a cage dipole in
> Helsinki in the mid-1980's. They had to give up their embassy building
> in the 1990's. It seems that it had been the Estonian embassy and the
> newly independent Estonians wanted it back.
>
>> (foreign to the country I was in) I would expect them to use encryption
>> whether by wire or by wireless, and to use wire most of the time.
>
> That depends much on the agreements between the foreign embassy and the
> host government. In most spots in Africa, leased lines are not an
> option. The choices are HF and satellite. HF is slow and subject to
> the vagaries of wave propagation. Encryption at HF adds overhead,
> slowing the data rate.
>
>> I
>> would think they might want to have a backup to wire. Wires after all
>> can be cut.
>
> That's why there's always a backup.
>
>
>> Many of the installations I have seen may well be left over
>> from the days when satellite comm links were not commonly available.
>
> ...or are the backups to leased lines or satellite communications.
>
>> Even so, I think it would be wise to maintain an HF backup to the
>> satellite system.
>
> There are also sat backups for sats. :-)
>
>> Additionally, some scheduled transmissions, perhaps
>> sending null messages, would be a good idea to make sure the system
>> works when it is really needed, and so that the sudden resumption of
>> transmission after none at all, would not reveal anything.
>
> There are always tests of backup systems and backup power.
>
>> Much
>> intelligence can be gleaned from traffic analysis, without decryption of
>> the traffic.
>
> Not so much, really. With the encryption, there is always a steady
> stream of data. Nothing can be gleaned by looking at the data stream.
> All one would see is a constant stream, day after day after day.
>
> Dave K8MN
>
>
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>
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