ZENDER OPSPORING IN AMSTERDAM.
                     Report regarding Direction Finding and operational conditions.
Since the middle of March 1945 the operators BRAM (Pieter de Vos) and DOUWE (Paul Peters) in Amsterdam have had many experiences with the German D.F. system. It was curious that other operators who worked in Amsterdam at the same time hardly had any trouble or none at all. If, however, BRAM or DOUWE went outside the town, then again they had at once the D.F. hot on their heels. From this they concluded, that D.F. was especially after these two operators, and probably recognised them by their sending methodes, finger prints and procedures. It is probably that the enemy desusted from accumulation of urgent traffic just before important events (as for instance just before and during the attack of the RAF at Huize Lydia, of which the Germans were informed, as was shown afterwards), that a good deal of the most important traffic during the last six months went through these operators.

Since the middle of March 1945 the Germans concentrated about 12 D.F. cars in Amsterdam.

It is known that at least three fixed D.F. stations were situated in different parts of the town, probably some more. Finally the enemy had at their disposal a great number of extremely well trained D.F. specialists. Our experiences showed that the enemy were able after the short time to be fully informed of our plans (
zendschema's).

Direction Finding cars would be stationed from about 9 o'clock in the morning until about 17.00 hours on several points in different quarters of the town, ready to come into action the moment one of us came into the air. They had wireless communication with their central-station. Without exception they were all driving on petrol, and thus they could easily recognised because all other German cars are obliged to use gas generators. The greater part of the D.F. cars belongs to the following type: half tons delivery vans, painted in German camouflage colours, the back part of the vans entirely closed except for some narrow air-conditioning slides in the middle. All these cars had a POL number, in the front part generally two uniformed Germans, of whom one would hold an earphone at the ear; at the back part were two specialists in civil clothes with the apparatus (
receiver).

Some WH as well as some WM car were used for this purpose. By extensive espionage by about 50 men during one week, we could trace the garages of nearly all cars, and several headquarters to which the specialists went with their reports at the end of the day.

Together with the KP (resistance figting units) of Amsterdam we made plans for the destruction of D.F. cars, fixed D.F. stations, and to capture alive one of their spcialists with his apparatus and reports. It was our intention to attack in one blow at least three cars, one fixed station and one specialist, by untimely action on own initiative of KP unit this plan however was frustrated, after which the German guarding and attentiv.... increased to such a degree that further actionwas almost impossible. Altogether two cars were attacked of which one burned out completely and the other one was slightly damaged. In this last case the car was attacked on the Museumplein under the eyes of hundreds of Germans. In both cases the ... of the cars get out uninjured, while the attackers escaped. A short time before the attack on the fixed D.F. station, in the middle of the Museumplein was planned, this station was removed by the Germans, so that the attack couldn't be executed. Since these attacks the Germans have only in rare cases risked to leave their cars parked in the streets, which of course hampered our look-out system. A couple of times it was seen that uniformed Germans with portable D.F. operators left the cars and walked round searchingly, after the cars had traced down roughtly the block of buildings from where it was transmitted. These Germans weare 'pulled down Eastern Front ear caps', great ... cellars turned up, cuffs pulled down so that earphones and leads were practically invisible. The apparatus was ... in a matehel er in a package wrapped in a piece of cloth.

When all methods mentioned above proved to be ineffective the Germans tried new methods. Twice it was reported that a car delivered a package at a house situated in the neighbourhood of the address from where transmission took place. Obviously the German had traced down with their fixed DF stations the approximate situation of the address without sending D.F. cars which would have warned us, afterwards rented a house nearby to try from there, invisible to our look-out system, to perform accurate D.F.

Since the beginning of April the Germans proceeded at last to a very effective measure, namely by putting strong interference on all HS (
Home-Station, England) and OS (Out-Station, Amsterdam) frequencies. Moreover, at least once they tried to mislead the Home-Station by making use of Out-Station frequency of same call sign, and then sending dummy messages (8th April). Under these circumstances continuation of regular contact is practically impossible, according to the procedures used until now.



Anti-measures.

Since the middle of March we frequently changed the addresses from where we transmitted. A doctor, ... Roman Catholic priest and a Protestant minister were asked to supply a regular amount of new addresses.

We asked for new plans and obtained them, but these gave no results.

Afterwards we transmitted a few times from two points situated in an angle of 90 degrees from a stationary D.F. station, known to us on different plans.

We also transmitted from two different points, situated as described above, after one another on the same plan, meanwhile contacting each other using broadcast receivers.. Fot this it was imperative to double our look-outs and patrolling staff.

A few times we worked from a point at least 18 km outside the town, covered by look-out system from approaches with telephonecommunication, in addition to look-out posts on church towers with field-glasses. By these measures we were able to transmit for a long time (i.e. 30th March). These addresses could only be used once. Moving- and transportdifficulties, lack of bicycles and searchings made these tasks extremely dangerous.

Traffic accumulation during April made it nesessary to transmit in the night, which due to increased look-out difficulty was very un ad..able.

As extention to the above described system, by which transmission found place from two different points on the same plan, we formed a new, so called T.D. Transmitting Dispersion), as follows: Central Post is connected via telehone lines with seven look-out posts. Via these telephone lines are assistents who operate the sets on the outposts, in telephone connection with the operator on the Central Post. In the meantime these line were used for long distance keying. For this purpose the Central Post put on the line a tension of 120 Volt, which set to work a relay at the other end of the line. By switching every few seconds from one outpost to another, sometimes using two outposts, at the same time , we hoped to confuse the German Direction Finding. For the communication and the construction of the technical part had we from the telephone service priority over all other commissions. At the same time we started te rebuild our sets, to construct relays, to instruct a certain number of assistants and ... seven times our look-out and patrolling staff. New crystals were asked for this purpose, five of each. Because it was essential that this methode remained secret, explosives (weight release switches) were fixed at the relays and the interior of the out-posts was so made that a complete transmitting station was found, in case of an enemy attack, as camouflage.

We wished in this way to prevent that attention was paid to the telephone line connection; but if found, it was impossible to discover the connection between telephone line and Central Post.

The T.D. system worked only on a limited extent.






     W/T intercept unit of the Ordungspolizei in Scheveningen.

                                           (Funkbeobachtunsstelle, or Fu-B-Stelle-Orpo)

                                                       By Hermann GISKES.

"Task of this unit was the tracing of, and listening to, enemy W/T traffic. Establishing, by listening, of W/T agents traffic, reception of two-way traffic, and determining the call-sings, and other traffic signals. The tracing of local enemy W/T agents by RDF methods. Arresting W/T agents in conjunction with the SiPo. The results of the above missions were reported to III-F for the purpose of analysis from an Abwehr point of view. In establishing W/T 'play' with the enemy, all technical data for the reception and establishment of traffic was procured, or dealt with, by Fu-B-Orpo, and the traffic of the agents concerned, or the official appointed to carry this out, was supervised by Fu-B-Orpo. The Fu-B-Stelle received the text of the W/T messages from the Stelle which was running the W/T 'play', i.e. II-F or the Sipo.

Between 1940 - 1943 Oberl. der Orpo
HEINRICH, was the O.C. from 1943 onwards was Hauptmann ...(name forgotten).

The Stelle had roughly 30 officials at it's disposition, the greater part being W/T and W/T intercept specialists. In 1943, HQ was transferred to Driebergen near Utrecht. In the autumn of 1944 a large portion of the technical material was lost in an air attack near Zwolle, whilst it was in the process of being transferred to Northern Holland.

The unit was equipped with a fluctuating number of RDF cars. Generally speaking, however there was only one at disposal. From 1942 onwards portable Nahpeiler (short range RDF sets) were operated, which are said to have produced good results.

Results obtained in the local RDFing of enemy W/T operators varied considerably. Sometimes the fixing of enemy W/T bases succeeded surprisingly quickly, in other cases many months often elapsed, and there were cases when no results were achieved at all. As a non-technical man the reasons for this are not clear to me. During 1942-1943, on the average, two or three active W/T agent sets were continually under observation. This figure increased gradually from the beginning of 1944 onwards.

I estimate that from the summer of 1941 until mid 1944 about 12 enemy agent transmitters in Holland were recognised, pin-pointed and captured through the purely technical means of the Fu-B-Stelle".







                                                           
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