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clean up and fixes
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m →Instrument Design: grammar correction (where to were)
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The ALSE instrument operated in two [[High Frequency|HF]] bands (5 MHz - HF1 - and 15 MHz - HF2) center frequencies and one [[VHF]] band (150 MHz), each with a bandwidth of 10% (using a [[chirp]]ed signal). The two HF bands shared the same center-feed [[dipole antenna]], while a 7 elements [[Yagi antenna]] was used for the VHF channel. Two different transceiver were used for the HF (alternating operation between HF1 and HF2 on a [[Pulse repetition frequency|PRF]]-by-[[Pulse repetition frequency|PRF]] basis) and VHF, sharing a common optical recorder. It was not possible to operate in VHF and HF simultaneously.
The whole system weighed 43 kg and required 103 W of power.
The electronics was located inside the [[Apollo Service Module]]. The two halves of the dipole antenna
Being the primary objective of the experiment the mapping of subsurface layers, the most critical trade-off in the design was that of penetration depth vs resolution: lower frequencies penetrates more, but allowed a smaller signal bandwidth and, therefore, a worst resolution which, in turn, affected the capability to discriminate subsurface echoes close to the surface.
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